MHagen's Quest for High-Altitude Performance (aka: Build Thread)

[M.Hagen]

Supercharger Selection & Installation

The M3 is a very capable car stock, but a consequence of the high-revving nature of the S65 is the low torque relative to its performance profile. Where I live and work, about 4300 feet above sea level, compromises the power even more. In an effort to help improve the engine’s performance, I decided to go with the Harrop TVS1740 supercharger kit combined with BPM's 91 octane tune.

Functionally, a roots style supercharger (Eaton TVS) will make the engine behave as if it was larger, as it is a fixed volume air pump. In essence, the TVS 1740 makes the S65 a 5.7L engine (3998cc + 1740cc). The characteristics of the power curve should be identical; a flat torque curve, and a peak horsepower near redline.

The Harrop Stage-1 is intended to output 6 to 6.5 psi, depending on breathing modifications. However, my situation will be different. A nice day with normal atmospheric pressure at sea level will be around 29.9 in-hg (14.7 psi). That same nice day at 4300 feet will be 24.5 in-hg (12.0 psi!!!). Since superchargers are a fixed to the crankshaft, the nominal pressure ratio is fixed. This means that I’ll only see around 2.8-3.2 psi (gauge pressure) with the same pulley setup as a sea level application

How the math works:
(actual barometric pressure + supercharger output) - standard atmospheric pressure = actual supercharger output

(11.2 psi + 6.5 psi) – 14.7 psi = 2.8 psi

I am very comfortable with breaking down engine bays and engines, so I decided to do the install myself. The Harrop kit has a fit and finish like OEM, the attention to detail is fantastic. I didn’t find any issues with the instructions or installation. I received very good feedback from @Nick//M3, as he also did the installation himself. One note for others to reference is that the DME wiring should be soldered in, not splice-connected.

The Harrop TVS kit is a very tidy package. The Supercharger unit itself is self-contained (does not require external oil connections) and mounts to the factory throttle-body assembly and an additional bracket tied into the thermostat housing.


OEM Plenum removed.


After first fire-up (ignore the dirty hand prints everywhere):


Driving impressions:

• First thing you notice is the whine. When others say it is present, they aren’t joking. In some ways I love it, but at the same time I wouldn’t mind it to be toned down a bit since it overwhelms the induction noise from the V8.
• If you roll into the throttle there is obviously more power. From about 50% throttle up, boost builds quickly and the torque is significant.
• If you roll into the throttle too quick, there is some hesitation. I’m hoping this can be tuned out. Mike has been responsive to my feedback and I’m confident we’ll get the calibration dialed in come spring time when snow tires come off.
• Traction through second gear is nonexistent with 275 PSS and TC off
• The overall powerband feels like before, but more. More torque, more power. It comes on quick and rides all the way to redline.

[M.Hagen]

Dyno & Initial Logs

I took my car to the dyno to get before and after numbers in order to get an accurate understanding of how much power the Harrop kit actually adds. There are a handful of dyno charts out there for Harrop kits, but none at altitude. All runs were performed at Turbo Lab in Orem, Utah. They have a DynoJet model 248x, with the new Dynojet RT datalogging stack and PowerCore software.

I did 4-5 runs at each of the three test levels I was interested in gathering data on. (1) Baseline, (2) Harrop on pump 91, and (3) Harrop on E85 blend (~E30-E35, ~95 octane).

Baseline Runs: 10/13/2016
Gear Used: 4 (DCT)
Ambient Temp: 67 F
Ambient Pressure: 25.5 in-hg (12.5 psi)
Humidity: 25%
Density Altitude: 6063 ft

Harrop Runs: 11/11/2016
Gear Used: 4 (DCT)
Ambient Temp: 72 F
Ambient Pressure:26.6 in-hg (13.0 psi)
Humidity: 26%
Density Altitude: 6129 ft

Red: Stock Baseline
Green: Harrop (pump 91 AKI)
Blue: Harrop (pump 91 AKI + E85 blended to 95 octane AKI)

Modifications:

• Harrop TVS1740 Stage-1 Kit
• BPM 91 Octane Tune
• Megan Rear Section (stock xpipe/cats)
• K&N Air Filter
• (spark pugs were changed ~2,000 miles before install)

Log of the green dyno run (pump 91 AKI):


Log of the blue dyno run (ethanol blend):

[M.Hagen]

RESERVED FOR SPRING 2017 DYNO/TUNE UPDATE







.

[M.Hagen]

RESERVED FOR PULLEY CHANGE / BOOST INCREASE FOR ALTITUDE COMPENSATION





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[pbonsalb]

That is what I would do -- change the pulley to compensate, assuming you do not ever need to go down to sea level.

[Mvy]

Welcome to the harrop club. You can reduce the noise of the whine by plugging your hood intakes(but just a little). Thought you might want to know you are pulling the same power and torque as I do at sea level. Have fun!

[SYT_Shadow]

thank you for the write up

What do you mean by solder the ecu connections? You have to physically modify the ecu?

I've driven several ess supercharged cars. Like you say, they feel like oem but much, much more hehe. The thing I don't like about them is losing the wonderful induction sound the engine makes

[M.Hagen]

Originally Posted by SYT_Shadow

What do you mean by solder the ecu connections? You have to physically modify the ecu?

One of the unique features on the Harrop kit that is absent from the other supercharger kits on the market is the addition of an electronic bypass valve. This valve essentially acts as a combination 'wastegate' and 'blow-off valve'. Therefore, the electronic bypass valve allows boost-bleed during certain conditions and allows for the pressure to be relieved when the throttle is closed.

To allow for this control, the electronic bypass valve needs access to relevant signals from the DME. I believe they are TPS and Throttle Actuator signals.

I'm still trying to wrap my head around this controller. It would be fun to get access to the controller to understand the logic.

[Pro-AM3]

no stage 2 numbers from Harrop yet?