Harrop Owners Chime In!

[MikeYQM]

Hi, my name is Mike and I have a problem. I have the boost bug.

I'm looking for feedback from any Harrop owners out there, I have a couple specific questions:

1. Are there any common bugs with the Harrop system? Either preventable through maintenance or otherwise?

2. Do you have any regrets after jumping on this system?

[B8bydesign]

Originally Posted by MikeYQM

Hi, my name is Mike and I have a problem. I have the boost bug.

I'm looking for feedback from any Harrop owners out there, I have a couple specific questions:

1. Are there any common bugs with the Harrop system? Either preventable through maintenance or otherwise?

2. Do you have any regrets after jumping on this system?

Good thread to read thru (if you haven't already) while you wait for responses:

https://www.m3post.com/forums/showthread.php?t=1070943

[ShakeNBake]

Do it! You won't regret it.

[drwankel]

I've had one for a few months with some decent seat time. Biggest issues/quirks are as follows:

1. The boost transition around 3.5k is a little funky sometimes. To put it better in perspective:

Originally Posted by eternallx

Anyone notice that if your applying maybe 50-60% throttle from the lower rpm ranges in lower gears its not very smooth alot of times. Mostly notice it when am trying to get out of a parking lot onto a busy highway quickly and the car would jerk as if power is coming on and off but not violently. My M is DCT.

Its sorta feels like the electronic bypass valve is closing and opening alot due to not applying the throttle super consistently so the engine is getting boost 1 second and not the next.

Originally Posted by BPMSport

This is the fueling going rich in case you slam your foot to the floor, and then leaning back out once it doesn't see full boost pressure. Will be ironed out in future revisions - we are doing some testing with different pressure sensors.

Need to update thread on progress with injectors and E85 - will chime in as soon as I can - but essentially I am having them flow tested to make sure the injector dead time/latency calculations are 100% spot on.

Originally Posted by Iyzmi

If I'm giving it half to three quarter throttle consistently from low RPM to high RPM without shifting it will sometimes "hesitate" until about 4k. It's hard to describe, but you can feel a noticeable step in power delivery. I thought it was transitioning VANOS profiles in a non-linear way but Mike's fueling explanation also makes sense. It's not a consistent issue and only occurs under partial throttle.

2. Its strongly recommended to remove the main cats when adding this kit. That has ramifications that may or may not be significant depending on your setup. In my case, I had a MPE exhaust, and adding test pipes made it sound like ass, so I now have to redo my exhaust setup. (probably going corsa)

3. The factory tire sizes cannot hold the power and torque this thing produces. Second gear is useless with the supercharger if you floor it. Depending on the conditions, you'll roast the tires in 3rd as well. You will need to think about how to get more rubber on the rear. Depending on your wheel setup - you may need to change wheels to run them properly.

That all being said, the rest of the kit is fantastic. Fit and finish is excellent. With the exception of quirk 1, its extremely smooth, and the power is great. Love the sound. I was expecting gas mileage to drop much more than it did. Do not regret getting the kit at all.

[MikeYQM]

Thanks for the info, I read some of that in my research.

1. The issue sounds an awful lot like a torque dip/hesitation issue I encountered when I installed my Bimmerworld X-Pipe between 2500-3000 RPM. This was mostly solved by tuning from Alpine and Epic for NA cars with a forward biased, catless X.

2. All cats are long gone. Corsa rear should be here mid March.

3. I'm running 275/35 19 rears now, was planning to go to 285/30 19 when these die. Would 295 be better for the rear?

Originally Posted by drwankel

I've had one for a few months with some decent seat time. Biggest issues/quirks are as follows:

1. The boost transition around 3.5k is a little funky sometimes. To put it better in perspective:

2. Its strongly recommended to remove the main cats when adding this kit. That has ramifications that may or may not be significant depending on your setup. In my case, I had a MPE exhaust, and adding test pipes made it sound like ass, so I now have to redo my exhaust setup. (probably going corsa)

3. The factory tire sizes cannot hold the power and torque this thing produces. Second gear is useless with the supercharger if you floor it. Depending on the conditions, you'll roast the tires in 3rd as well. You will need to think about how to get more rubber on the rear. Depending on your wheel setup - you may need to change wheels to run them properly.

That all being said, the rest of the kit is fantastic. Fit and finish is excellent. With the exception of quirk 1, its extremely smooth, and the power is great. Love the sound. I was expecting gas mileage to drop much more than it did. Do not regret getting the kit at all.

[drwankel]

Originally Posted by MikeYQM

Thanks for the info, I read some of that in my research.

1. The issue sounds an awful lot like a torque dip/hesitation issue I encountered when I installed my Bimmerworld X-Pipe between 2500-3000 RPM. This was mostly solved by tuning from Alpine and Epic for NA cars with a forward biased, catless X.

2. All cats are long gone. Corsa rear should be here mid March.

3. I'm running 275/35 19 rears now, was planning to go to 285/30 19 when these die. Would 295 be better for the rear?

Issue number 1 is solely related to the fact that the map sensor can't read boost from what I understood. Unknown if this is going to get a real fix. Its been talked about, but the reality is the market for these cars is shrinking as they get older. The business case for the R+D to get this fixed right is hard to justify because this isn't a simple fix. Once you have this new data, you have to do something with it which means significant changes to the DME programming, and maybe harrops control module. Just my own speculation here.

With issue number 3, if you have 10" wide rears, 285/30s are really the widest you should be running. The problem is there isn't alot of tire selection in this size. Michelin PS4S is not available in this size for example. PSS is, but that's the older compound. You can run 295s on the rear, but its not ideal. That may be what I end up doing anyway, as I don't think going from a 265 to a 275 is going really improve things, and I really want my 2nd gear back.

[Adriano917]

You haven’t considered ESS G1 or VF ?

[DrFerry]

Originally Posted by MikeYQM

Hi, my name is Mike and I have a problem. I have the boost bug. I'm looking for feedback from any Harrop owners out there, I have a couple specific questions:

1. Are there any common bugs with the Harrop system? Either preventable through maintenance or otherwise?

2. Do you have any regrets after jumping on this system?

As B8bydesign already mentioned, most issues are chronicled here:
https://www.m3post.com/forums/showthread.php?t=1070943

Studying that thread should give you a good feel for what others have already experienced.

Regarding your questions:

1 and 1.5: I have owned mine since late 2015 and have over 50K miles on my Harrop system. I recently encountered a bad electrical connection that was related to the poor quality of the shop installation. In my experience, there are no common bugs that I know of with the system (kit). Owners have mentioned some occasional lower speed drivability concerns, below or around the 3500RPM boost transition zone, and this is discussed in other posts. I have found this particular issue can be mitigated with throttle map selection (I use Sport). Additionally, increased E85 fuel concentration also seems to help (about E20+). The low speed drivability boost transition issue really isn’t that noticeable, except occasionally when the throttle position and RPMs ‘just happen’ to be exactly right.

The Harrop “system” has turned out to be very robust indeed in my opinion. That being said the serpentine belt can slip if the belt tensioner is old (weak). A Gatorback style serpentine belt (Conti Elite) helped greatly reduce SC belt slippage on mine (also mentioned in the thread). One of the Harrop serpentine belt carrier bearings on my system has now become noisy (after 50K miles), but after removing and oiling, it is now much less noisy. Other owners (including me) have noticed what they thought was thermostat housing gasket coolant seepage - since the housing bolts are used in securing a carrier bracket. However, this issue turned out to be a worn header tank return hose (which needed replacing) rather than the gasket or thermostat housing itself. Overall, and in summary, the Harrop super charger system is a very robust and well-engineered kit well proven at the Nurburgring and on track.

In order to avoid any disappointment, or issues later on down the road, I recommend choosing a high quality shop and preferably one that has installed a Harrop kit before. IF that is not possible - and you are mechanically capable, then consider installing the kit yourself. Become very familiar with the installation guide before making your choice of DIY or shop selection. This is very important. See installation guide file attached.

In order to maximize your return on investment I recommend doing and/or considering most if not all of the following listed below:

A) Install an X-Pipe where the primary CATS are removed and has 200 cells per square inch (CPSI) high flow cat secondaries with resonators.
B) OR - if not A) above then Install a Catless, resonated X-Pipe
C) Replace the spark plugs with either new OEM or one heat range colder as used by G-Power and other kits (see my signature for alternative NGK Racing plug specs). I already feel the heat for blaspheming against the OEM plugs.
D) Can keep the stock OEM rear exhaust box to reduce costs if desired.
E) Replace (renew) all four oxygen sensors
F) Use a Continental Elite Gatorback serpentine pulley drive belt (see thread)
G) Use a high flow air filter like the Piper-Cross (helicopter style so I’m told)
H) Invest in some wider rear wheels; preferably 11X18 with ET 32. Put your OEM 9.5 inch wide rear wheels onto the front axle to reduce the cost of buying four new wheels.
I) To increase mechanical rear axle grip install at least 295 section width summer tires of at least UTQG Treadwear = 300 or lower. I use 295/35R18 Michelin PSS. Combine the new tires with slightly lower cold inflation pressures to increase the size (surface area) of the contact patch (the size of which is simply the load on the tire divided by its inflation pressure). With the bigger tire carcass envelope, 32 psi cold seems to work okay for me. Though I have run lower at the cost of increased shoulder wear.
J) Ensure differential oil and transmission oil are full and in good condition or relatively new.
K) Ensure your rod bearings and engine mounts are either new, low mileage and/or in decent shape.
L) Can add a couple of gallons of E85 to a full tank of 93 Octane E10 to get the most horsepower from the kit in my experience (especially in summer).

2) Regrets
A) You will spend more money on fuel
B) Tire consumption will increase
C) While using drag radials, my DCT clutch started to slip so it had to be upgraded to SSP Spec-R
D) SC whine was a bit loud for me so I blocked off the hood air box inlet and rely solely upon the front bumper air box inlet which quietened things down a bit.
E) The 14-hour time difference between the USA and Australia, but now Harrop have a U.S. Sales office in Ohio for parts (if ever needed).

3) Smiles
A) The Harrop kit will bring you many smiles. It makes the S65 V8 think it’s a V10.
B) I once combined the Harrop with high grip drag radials on the street for extra giggles.
C) On cooler days (say below 45F) this kit seems to find an extra 20 or 30 horsepower…
D) Mike Benvo. He’s the best for customer service and help with the system.

I’ve given you a lot here to think about. I hope this helps you and other people.

[FC5]

Originally Posted by DrFerry

As B8bydesign already mentioned, most issues are chronicled here:
https://www.m3post.com/forums/showthread.php?t=1070943

Studying that thread should give you a good feel for what others have already experienced.

Regarding your questions:

1 and 1.5: I have owned mine since late 2015 and have over 50K miles on my Harrop system. I recently encountered a bad electrical connection that was related to the poor quality of the shop installation. In my experience, there are no common bugs that I know of with the system (kit). Owners have mentioned some occasional lower speed drivability concerns, below or around the 3500RPM boost transition zone, and this is discussed in other posts. I have found this particular issue can be mitigated with throttle map selection (I use Sport). Additionally, increased E85 fuel concentration also seems to help (about E20+). The low speed drivability boost transition issue really isn’t that noticeable, except occasionally when the throttle position and RPMs ‘just happen’ to be exactly right.

The Harrop “system” has turned out to be very robust indeed in my opinion. That being said the serpentine belt can slip if the belt tensioner is old (weak). A Gatorback style serpentine belt (Conti Elite) helped greatly reduce SC belt slippage on mine (also mentioned in the thread). One of the Harrop serpentine belt carrier bearings on my system has now become noisy (after 50K miles), but after removing and oiling, it is now much less noisy. Other owners (including me) have noticed what they thought was thermostat housing gasket coolant seepage - since the housing bolts are used in securing a carrier bracket. However, this issue turned out to be a worn header tank return hose (which needed replacing) rather than the gasket or thermostat housing itself. Overall, and in summary, the Harrop super charger system is a very robust and well-engineered kit well proven at the Nurburgring and on track.

In order to avoid any disappointment, or issues later on down the road, I recommend choosing a high quality shop and preferably one that has installed a Harrop kit before. IF that is not possible - and you are mechanically capable, then consider installing the kit yourself. Become very familiar with the installation guide before making your choice of DIY or shop selection. This is very important. See installation guide file attached.

In order to maximize your return on investment I recommend doing and/or considering most if not all of the following listed below:

A) Install an X-Pipe where the primary CATS are removed and has 200 cells per square inch (CPSI) high flow cat secondaries with resonators.
B) OR - if not A) above then Install a Catless, resonated X-Pipe
C) Replace the spark plugs with either new OEM or one heat range colder as used by G-Power and other kits (see my signature for alternative NGK Racing plug specs). I already feel the heat for blaspheming against the OEM plugs.
D) Can keep the stock OEM rear exhaust box to reduce costs if desired.
E) Replace (renew) all four oxygen sensors
F) Use a Continental Elite Gatorback serpentine pulley drive belt (see thread)
G) Use a high flow air filter like the Piper-Cross (helicopter style so I’m told)
H) Invest in some wider rear wheels; preferably 11X18 with ET 32. Put your OEM 9.5 inch wide rear wheels onto the front axle to reduce the cost of buying four new wheels.
I) To increase mechanical rear axle grip install at least 295 section width summer tires of at least UTQG Treadwear = 300 or lower. I use 295/35R18 Michelin PSS. Combine the new tires with slightly lower cold inflation pressures to increase the size (surface area) of the contact patch (the size of which is simply the load on the tire divided by its inflation pressure). With the bigger tire carcass envelope, 32 psi cold seems to work okay for me. Though I have run lower at the cost of increased shoulder wear.
J) Ensure differential oil and transmission oil are full and in good condition or relatively new.
K) Ensure your rod bearings and engine mounts are either new, low mileage and/or in decent shape.
L) Can add a couple of gallons of E85 to a full tank of 93 Octane E10 to get the most horsepower from the kit in my experience (especially in summer).

2) Regrets
A) You will spend more money on fuel
B) Tire consumption will increase
C) While using drag radials, my DCT clutch started to slip so it had to be upgraded to SSP Spec-R
D) SC whine was a bit loud for me so I blocked off the hood air box inlet and rely solely upon the front bumper air box inlet which quietened things down a bit.
E) The 14-hour time difference between the USA and Australia, but now Harrop have a U.S. Sales office in Ohio for parts (if ever needed).

3) Smiles
A) The Harrop kit will bring you many smiles. It makes the S65 V8 think it’s a V10.
B) I once combined the Harrop with high grip drag radials on the street for extra giggles.
C) On cooler days (say below 45F) this kit seems to find an extra 20 or 30 horsepower…
D) Mike Benvo. He’s the best for customer service and help with the system.

I’ve given you a lot here to think about. I hope this helps you and other people.

Awesome post, I appreciate you taking the time to write such an insightful response with detailed info for those looking to purchasing this kit such as myself.

Question regarding A and/or B, which brands/models can you suggest? I currently have Remus Race axleback which I love, but admittedly is a bit loud, I was thinking about adding a Fabspeed X-pipe. May I ask what exhaust setup you are running? EDIT: I guess I should've read your signature first! lol

[DrFerry]

Originally Posted by FC5

Awesome post, I appreciate you taking the time to write such an insightful response with detailed info for those looking to purchasing this kit such as myself.

Question regarding A and/or B, which brands/models can you suggest? I currently have Remus Race axleback which I love, but admittedly is a bit loud, I was thinking about adding a Fabspeed X-pipe. May I ask what exhaust setup you are running? EDIT: I guess I should've read your signature first! lol

Good catch. Yes I chose to use the M3-World X-Pipe with 200 cpsi High Flow Cats & Custom Resonators. It's a polished stainless steel piece - and of high quality in my opinion. The longevity of the high flow cats is important to me. Fabspeed also make some excellent stuff. I use the stock OEM back muffler box for quietness when cruising and during normal driving. However, as soon as one steps on the throttle the sound is plenty loud for my tastes. Here are a few sound clip links to some Soundcloud files I made some years ago with the M3-World X-Pipe as well as the Harrop.

Sound Clips:

X-Pipe Exterior
https://soundcloud.com/user-90547482...ipe-exterior-1

X-Pipe Exterior
https://soundcloud.com/user-90547482/m3-x-pipe-exterior

X-Pipe Interior
https://soundcloud.com/user-90547482/m3-x-pipe-interior

There are some other sound clips on this page too:
https://soundcloud.com/user-90547482

Hope these help.
PS: $1 USA = ~$1.3 AUD (as of 2/26/'21) and AUS is a free trade zone with the USA so no import taxes. Member DaveDee owns the business.

https://m3world.com.au/shop/exhaust-...catsresonator/

[FC5]

Originally Posted by DrFerry

Good catch. Yes I chose to use the M3-World X-Pipe with 200 cpsi High Flow Cats & Custom Resonators. It's a polished stainless steel piece - and of high quality in my opinion. The longevity of the high flow cats is important to me. Fabspeed also make some excellent stuff. I use the stock OEM back muffler box for quietness when cruising and during normal driving. However, as soon as one steps on the throttle the sound is plenty loud for my tastes. Here are a few sound clip links to some Soundcloud files I made some years ago with the M3-World X-Pipe as well as the Harrop.

Sound Clips:

X-Pipe Exterior
https://soundcloud.com/user-90547482...ipe-exterior-1

X-Pipe Exterior
https://soundcloud.com/user-90547482/m3-x-pipe-exterior

X-Pipe Interior
https://soundcloud.com/user-90547482/m3-x-pipe-interior

There are some other sound clips on this page too:
https://soundcloud.com/user-90547482

Hope these help.
PS: $1 USA = ~$1.3 AUD (as of 2/26/'21) and AUS is a free trade zone with the USA so no import taxes. Member DaveDee owns the business.

https://m3world.com.au/shop/exhaust-...catsresonator/

Sounds wicked! That definitely helps, thank you again!

[MikeYQM]

Originally Posted by DrFerry

As B8bydesign already mentioned, most issues are chronicled here:
https://www.m3post.com/forums/showthread.php?t=1070943

Studying that thread should give you a good feel for what others have already experienced.

Regarding your questions:

1 and 1.5: I have owned mine since late 2015 and have over 50K miles on my Harrop system. I recently encountered a bad electrical connection that was related to the poor quality of the shop installation. In my experience, there are no common bugs that I know of with the system (kit). Owners have mentioned some occasional lower speed drivability concerns, below or around the 3500RPM boost transition zone, and this is discussed in other posts. I have found this particular issue can be mitigated with throttle map selection (I use Sport). Additionally, increased E85 fuel concentration also seems to help (about E20+). The low speed drivability boost transition issue really isn't that noticeable, except occasionally when the throttle position and RPMs 'just happen' to be exactly right.

The Harrop "system" has turned out to be very robust indeed in my opinion. That being said the serpentine belt can slip if the belt tensioner is old (weak). A Gatorback style serpentine belt (Conti Elite) helped greatly reduce SC belt slippage on mine (also mentioned in the thread). One of the Harrop serpentine belt carrier bearings on my system has now become noisy (after 50K miles), but after removing and oiling, it is now much less noisy. Other owners (including me) have noticed what they thought was thermostat housing gasket coolant seepage - since the housing bolts are used in securing a carrier bracket. However, this issue turned out to be a worn header tank return hose (which needed replacing) rather than the gasket or thermostat housing itself. Overall, and in summary, the Harrop super charger system is a very robust and well-engineered kit well proven at the Nurburgring and on track.

In order to avoid any disappointment, or issues later on down the road, I recommend choosing a high quality shop and preferably one that has installed a Harrop kit before. IF that is not possible - and you are mechanically capable, then consider installing the kit yourself. Become very familiar with the installation guide before making your choice of DIY or shop selection. This is very important. See installation guide file attached.

In order to maximize your return on investment I recommend doing and/or considering most if not all of the following listed below:

A) Install an X-Pipe where the primary CATS are removed and has 200 cells per square inch (CPSI) high flow cat secondaries with resonators.
B) OR - if not A) above then Install a Catless, resonated X-Pipe
C) Replace the spark plugs with either new OEM or one heat range colder as used by G-Power and other kits (see my signature for alternative NGK Racing plug specs). I already feel the heat for blaspheming against the OEM plugs.
D) Can keep the stock OEM rear exhaust box to reduce costs if desired.
E) Replace (renew) all four oxygen sensors
F) Use a Continental Elite Gatorback serpentine pulley drive belt (see thread)
G) Use a high flow air filter like the Piper-Cross (helicopter style so I'm told)
H) Invest in some wider rear wheels; preferably 11X18 with ET 32. Put your OEM 9.5 inch wide rear wheels onto the front axle to reduce the cost of buying four new wheels.
I) To increase mechanical rear axle grip install at least 295 section width summer tires of at least UTQG Treadwear = 300 or lower. I use 295/35R18 Michelin PSS. Combine the new tires with slightly lower cold inflation pressures to increase the size (surface area) of the contact patch (the size of which is simply the load on the tire divided by its inflation pressure). With the bigger tire carcass envelope, 32 psi cold seems to work okay for me. Though I have run lower at the cost of increased shoulder wear.
J) Ensure differential oil and transmission oil are full and in good condition or relatively new.
K) Ensure your rod bearings and engine mounts are either new, low mileage and/or in decent shape.
L) Can add a couple of gallons of E85 to a full tank of 93 Octane E10 to get the most horsepower from the kit in my experience (especially in summer).

2) Regrets
A) You will spend more money on fuel
B) Tire consumption will increase
C) While using drag radials, my DCT clutch started to slip so it had to be upgraded to SSP Spec-R
D) SC whine was a bit loud for me so I blocked off the hood air box inlet and rely solely upon the front bumper air box inlet which quietened things down a bit.
E) The 14-hour time difference between the USA and Australia, but now Harrop have a U.S. Sales office in Ohio for parts (if ever needed).

3) Smiles
A) The Harrop kit will bring you many smiles. It makes the S65 V8 think it's a V10.
B) I once combined the Harrop with high grip drag radials on the street for extra giggles.
C) On cooler days (say below 45F) this kit seems to find an extra 20 or 30 horsepower…
D) Mike Benvo. He's the best for customer service and help with the system.

I've given you a lot here to think about. I hope this helps you and other people.

Thanks for the input and details!

I am already running a Bimmerworld X-Pipe (catless) soon to be paired with a Corsa exhaust.

I have the ZCP 359M wheels, 10" rears so I *think* I can run 295/70 PS4S.

All fluids are new as of last winter (10k km ago) along with new upstream O2 and plugs which would get replaced next winter as part of my schedule.

E85 and 93 octane are not options around here and likely never will be so I'm definitely limited there.

[MikeYQM]

Originally Posted by DrFerry

As B8bydesign already mentioned, most issues are chronicled here:
https://www.m3post.com/forums/showthread.php?t=1070943

Studying that thread should give you a good feel for what others have already experienced.

Regarding your questions:

1 and 1.5: I have owned mine since late 2015 and have over 50K miles on my Harrop system. I recently encountered a bad electrical connection that was related to the poor quality of the shop installation. In my experience, there are no common bugs that I know of with the system (kit). Owners have mentioned some occasional lower speed drivability concerns, below or around the 3500RPM boost transition zone, and this is discussed in other posts. I have found this particular issue can be mitigated with throttle map selection (I use Sport). Additionally, increased E85 fuel concentration also seems to help (about E20+). The low speed drivability boost transition issue really isn't that noticeable, except occasionally when the throttle position and RPMs 'just happen' to be exactly right.

The Harrop "system" has turned out to be very robust indeed in my opinion. That being said the serpentine belt can slip if the belt tensioner is old (weak). A Gatorback style serpentine belt (Conti Elite) helped greatly reduce SC belt slippage on mine (also mentioned in the thread). One of the Harrop serpentine belt carrier bearings on my system has now become noisy (after 50K miles), but after removing and oiling, it is now much less noisy. Other owners (including me) have noticed what they thought was thermostat housing gasket coolant seepage - since the housing bolts are used in securing a carrier bracket. However, this issue turned out to be a worn header tank return hose (which needed replacing) rather than the gasket or thermostat housing itself. Overall, and in summary, the Harrop super charger system is a very robust and well-engineered kit well proven at the Nurburgring and on track.

In order to avoid any disappointment, or issues later on down the road, I recommend choosing a high quality shop and preferably one that has installed a Harrop kit before. IF that is not possible - and you are mechanically capable, then consider installing the kit yourself. Become very familiar with the installation guide before making your choice of DIY or shop selection. This is very important. See installation guide file attached.

In order to maximize your return on investment I recommend doing and/or considering most if not all of the following listed below:

A) Install an X-Pipe where the primary CATS are removed and has 200 cells per square inch (CPSI) high flow cat secondaries with resonators.
B) OR - if not A) above then Install a Catless, resonated X-Pipe
C) Replace the spark plugs with either new OEM or one heat range colder as used by G-Power and other kits (see my signature for alternative NGK Racing plug specs). I already feel the heat for blaspheming against the OEM plugs.
D) Can keep the stock OEM rear exhaust box to reduce costs if desired.
E) Replace (renew) all four oxygen sensors
F) Use a Continental Elite Gatorback serpentine pulley drive belt (see thread)
G) Use a high flow air filter like the Piper-Cross (helicopter style so I'm told)
H) Invest in some wider rear wheels; preferably 11X18 with ET 32. Put your OEM 9.5 inch wide rear wheels onto the front axle to reduce the cost of buying four new wheels.
I) To increase mechanical rear axle grip install at least 295 section width summer tires of at least UTQG Treadwear = 300 or lower. I use 295/35R18 Michelin PSS. Combine the new tires with slightly lower cold inflation pressures to increase the size (surface area) of the contact patch (the size of which is simply the load on the tire divided by its inflation pressure). With the bigger tire carcass envelope, 32 psi cold seems to work okay for me. Though I have run lower at the cost of increased shoulder wear.
J) Ensure differential oil and transmission oil are full and in good condition or relatively new.
K) Ensure your rod bearings and engine mounts are either new, low mileage and/or in decent shape.
L) Can add a couple of gallons of E85 to a full tank of 93 Octane E10 to get the most horsepower from the kit in my experience (especially in summer).

2) Regrets
A) You will spend more money on fuel
B) Tire consumption will increase
C) While using drag radials, my DCT clutch started to slip so it had to be upgraded to SSP Spec-R
D) SC whine was a bit loud for me so I blocked off the hood air box inlet and rely solely upon the front bumper air box inlet which quietened things down a bit.
E) The 14-hour time difference between the USA and Australia, but now Harrop have a U.S. Sales office in Ohio for parts (if ever needed).

3) Smiles
A) The Harrop kit will bring you many smiles. It makes the S65 V8 think it's a V10.
B) I once combined the Harrop with high grip drag radials on the street for extra giggles.
C) On cooler days (say below 45F) this kit seems to find an extra 20 or 30 horsepower…
D) Mike Benvo. He's the best for customer service and help with the system.

I've given you a lot here to think about. I hope this helps you and other people.

Do you have a part number for the Gatorback off hand? All I have found in the Gatorback style belt is Goodyear in 6PK1900

[tbuck]

In for the response for belt info as well, needing to get one of these too.

Also I asked Mike Benvo specifically about the plugs and possible need for a cooler model and he assured me that stock were perfectly fine for street use. I have had to use cooler plugs in other SC applications before so was curious.

[Fastalpine]

I would also be curious which belt

[MikeYQM]

From what I could find in my research:

Belt size is 6PK1905.

Goodyear/Conti Elite part number is: 4060750

I believe Goodyear/Conti discontinued that spec in the Gatorback/Elite belt. I could only find 6pk1900G in current production.

I ordered one Conti 4060750 on Amazon but revived a non-Gatorback version. I found them on eBay which appear to be NOS Gatorback/Elite 4060750 so I ordered two and am hopeful.

[tbuck]

Originally Posted by MikeYQM

From what I could find in my research:

Belt size is 6PK1905.

Goodyear/Conti Elite part number is: 4060750

I believe Goodyear/Conti discontinued that spec in the Gatorback/Elite belt. I could only find 6pk1900G in current production.

I ordered one Conti 4060750 on Amazon but revived a non-Gatorback version. I found them on eBay which appear to be NOS Gatorback/Elite 4060750 so I ordered two and am hopeful.

Yeah, I am seeing a number of vendors with that belt but I am very wary of getting things on eBay. If you do get the right part can you post the seller here? Thanks for being the Guinee pig, lol!

[MikeYQM]

Will confirm one way or the other for sure.

[tbuck]

Originally Posted by MikeYQM

Will confirm one way or the other for sure.

Hey, just checking if you got the right belt on not? I am about to get one as well and just wanted to see what you got. Thanks!

[MikeYQM]

The belts arrived today. 6PK1905 in Gatorback!!

[Fastalpine]

Originally Posted by MikeYQM

The belts arrived today. 6PK1905 in Gatorback!!

Which one specifically did you order to get a gatorback version?

[DrFerry]

Originally Posted by MikeYQM

Do you have a part number for the Gatorback off hand? All I have found in the Gatorback style belt is Goodyear in 6PK1900

Yes, sorry for the late reply. I rarely come here nowadays. I used: Continental Elite part = 4060747