The realities, do's and dont's of boosting a 1985 928 5SPD - Rennlist Discussion Forums



The realities, do's and dont's of boosting a 1985 928 5SPD

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Old 03-16-2017, 08:01 PM   #1
cpayne
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Default The realities, do's and dont's of boosting a 1985 928 5SPD

Greetings fellow boosters! Correction!, I'm not actually creating any boost yet, so I'm not in your ranks yet, but I want to be. I created this thread to chronicle my adventure of boosting my 1985 928 S 5 Speed car.

The hope is that all the knowledgeable folks that have been down the road I'm travelling can chime in and share their wisdom and all the do's and don'ts of boosting a 928.

To learn the back story about the car and it's general rehabilitation please read this thread:
http://rennlist.com/forums/928-forum...rom-texas.html

About the Turbo kit. Built and installed by Mark Robinson in Austin Texas.

See MAF harness and Turbo Design Documents (Currently 3 page pdf Will scan again on a plotter at work to make it 1 page)
https://drive.google.com/open?id=0B-...zJZbFVMWVZoLXc

The turbo kit is made of of the following components:
Mid mounted Precision Billet 62mm with a T04 hot housing with a .96AR
A new stainless still exhaust with a CAT delete.
30 LB injectors
Wide band O2.
Boost controller (Yet to be installed)
Fuel rail pressure gauge.
Vacuum gauge.
Oil scavenge pump (Cheap and loud, I'm replacing with a gear driven pump)

Mark was also hired to perform a top end refresh, new plugs, wires distributors rotor . Temp II was replaced as was normal band 02.
Car would start and run rough and when hot wouldn't start again.

AFR was at 10-12
MAF checked out at 382
idle is at 1100
Timing was retarded to 14deg

After some powder coat removal on the WB AFR is 14.9-15.00 but bounces to max on occasion. Starts when warm now.

Paid for Mark to tune on dyno to 450 - 500 HP and have non det chips put in.

Dyno and tuning did not happen. The specs on the chips are as follows "Taken from a chat with Mark " " Just the EZK chip was designed by me with Boostlogic and then mapped and burned by John specifically for a turbocharged (not supercharged) 928S 32v 85-86.

Marks suggestions on tuning "The car won't feel "strong" until the air-fuels are normal on the Wideband: you wanna see 11.8-12.0 on-boost. Readings while cruising should be 14.7-ish with O2 corrections"
you can "trim" the air/fuel via an adjustable fuel pressure regulator, to ensure you're at about 12:1 A/F ratio while on-boost.

"You should not be able to completely tune without a SharkTuner: which I once had access to & the interface for (came damaged from Speake). But fuel trimming while on-boost can be done by adjusting the fuel pressure up/down as-needed indicative of your measured AF ratio while on the dyno (or while driving). Start off in 2nd gear and make your first adjustment: if it goes above 13.5; stop your run and enrichen & then try again. once you have 2nd gear mastered, then go for 3rd: closely watching the AF gauge. while in 3rd, if it goes richer than 13.3, stop the run and enriching (increase fuel pressure by screwing the set-screw in: 1/4 turn = 1psi fuel pressure increase). Once 3rd is mastered, then try 4th if you dare venture that fast "

I was put in touch with a gentlemen named Pele , who has the same MY ,Engine 5spd trans and the same kit by Mark . He has a Shark tuner and has spent several years tuning his car. I paid him to burn me a set of chips and we believe that if I make some adjustments to my kit, to match his setup, then I'll be much closer that I am now. I have also reach out to John Speake and will purchase my own Shark tuner.

Here is what I have to do to get my kit to match Pele's kit add a an 1987 MY FPR.
Move the MAF from the rear of the car to its original position.
Install the chipset for EZK and FH.
Set the MAF CO and Idle.
Find an intercooler
Install the new Scavenge pump "Can be done later"
Install the Boost Controller

Here are some videos of the turbo.
https://www.youtube.com/playlist?lis...KVoVUzzhd9S5Bi

Last edited by cpayne; 03-17-2017 at 08:44 PM. Reason: Added Turbo Design Document Links
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Old 03-16-2017, 09:26 PM   #2
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Why was the maf put there?
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Old 03-16-2017, 09:54 PM   #3
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Why was the maf put there?
Opinions vary on this.

Many feel you should only draw through a MAF, it is how most OEM boosted applications are setup with the MAF before the compressor.

However, I'm not sure any OEM system has quite that much piping between the MAF & Throttle body, that poses a unique issue to this theory.

It has also been proven that boosted 928's work just fine with the MAF after the compressor. So I agree he should put it back in the stock location, it greatly simplifies the setup.

If you are trying to design a closed oil vapor system, the MAF should be before the compressor since the oil breather line needs to be before the compressor too (or you will pressurize the crankcase, very bad). If the MAF is after the breather, you run the risk of fouling the MAF wire.
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Old 03-16-2017, 09:56 PM   #4
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Good luck on your quest!
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Old 03-16-2017, 11:10 PM   #5
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Quote:
Originally Posted by Hacker-Pschorr View Post
Opinions vary on this.

Many feel you should only draw through a MAF, it is how most OEM boosted applications are setup with the MAF before the compressor.

However, I'm not sure any OEM system has quite that much piping between the MAF & Throttle body, that poses a unique issue to this theory.

It has also been proven that boosted 928's work just fine with the MAF after the compressor. So I agree he should put it back in the stock location, it greatly simplifies the setup.

If you are trying to design a closed oil vapor system, the MAF should be before the compressor since the oil breather line needs to be before the compressor too (or you will pressurize the crankcase, very bad). If the MAF is after the breather, you run the risk of fouling the MAF wire.
Here is Marks philosophy on why it was moved to the rear.
"it was never really forced air: merely a higher pressure area in front of the radiator: there's no seal in the intake system therefore no real "ram-air". Lots of "tests" & theories out there on this. the 928 had a good setup. For any MAF system, the MAF needs to be located where the air filter won't interfere with it's operation & where the turbo re-circ is angled so that it doesn't cause turbulence that could alter it's signal."
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Old 03-16-2017, 11:30 PM   #6
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With the MAF in the stock location and a single 90 degree bend before the MAF, you can run into issues with uneven air flow across the wire. Symptoms are confused idle and / or slight surging under cruise. People may have run into other issues, these are the primary ones I dealt with.

In the Murf928 setup, the inter-cooler sitting directly over the MAF takes care of this problem (same as the stock air filter does):
http://rennlist.com/forums/928-forum...s-new-car.html

For the non-intercooled units, the MAF air diffuser is used on top of the MAF.

Also need to remember any air or boost leak before the MAF isn't as big of an issue as a leak after the MAF. If you are bleeding off metered air, the computers cannot properly send the correct fuel and ignition signals through the system.
With that much plumbing after the MAF (in the rear location) this increases the potential for leak induced issues by a huge factor. For this reason alone I would keep it in the stock location.

On that note, I'm talking to Todd about the cost of making a few of those intercoolers since a couple people have inquired about them. Fits L-Jet and 85/86 cars. Possible S4's in the not to distant future.......
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Old 03-17-2017, 12:10 AM   #7
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Quote:
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On that note, I'm talking to Todd about the cost of making a few of those intercoolers since a couple people have inquired about them. Fits L-Jet and 85/86 cars. Possible S4's in the not to distant future.......
I'm needing to add an inter cooler. If he makes them I would be in for one.

I called boost Logic in Austin as Pele's setup uses one they Made for Mark Robinson for around 700.00. Unfortunately they were not interested in custom work. Here is a pic of Pele's inter cooler really nice. He was kind enough to shoot a video of his engine bay in trying to help me make my setup the same as his. Currently I will be missing the inter cooler. I have to check, but I thinking I'm missing the blow off valve too.
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Old 03-17-2017, 12:23 AM   #8
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Couple things to note from that video

1. The intercooler made by turbo Todd could possibly be modified so the pipe coming from the turbo would go directly into the cooler. That would make for a pretty nice setup, very clean looking engine bay.
Where that pipe comes up along the firewall, it appears turning that elbow 90 degrees could be very close to mating up to the IC. This is an air / water IC (one in the video is air / air). I'm not going to dig up old arguments about which one is better. This is simply what we decided to make for all the Murf928 kits. The IC uses a water pump attached to the windshield washer resivior and that fluid to pump through the system with a heat exchanger in front of the radiator. Very simple to route the rubber heater hose.

2. He's using meth injection so that will effect the map on your car if you don't have that.

3. The intake air temp sensor - the stock one is useless. Reacts way too slow to be useful. There is another Bosh unit that is a direct fit (used in almost every VW) which is fast acting and can be mapped in the shark tuner to actually be a benefit by reducing timing if your intake temps go too high. Using the stock sensor you might as well just disable it and tune accordingly.
If memory serves we added the sensor in question to one of the intake plenums in Shane's car.
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Old 03-17-2017, 12:47 AM   #9
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Quote:
Originally Posted by Hacker-Pschorr View Post
Couple things to note from that video

2. He's using meth injection so that will effect the map on your car if you don't have that.


3. The intake air temp sensor - the stock one is useless. Reacts way too slow to be useful. There is another Bosh unit that is a direct fit (used in almost every VW) which is fast acting and can be mapped in the shark tuner to actually be a benefit by reducing timing if your intake temps go too high. Using the stock sensor you might as well just disable it and tune accordingly.
If memory serves we added the sensor in question to one of the intake plenums in Shane's car.
I'll confirm, but I think the tune he put on the chips he burned for me are pre meth injection.

I'm interested in the water/air intercooler. Keep me posted on Todds willingness to make some.

What is the part number for the temp sensor you refer too?
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Old 03-17-2017, 01:37 AM   #10
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We had a local (not on RL) who had an 85 5 spd turbo'd by Mark a few years ago. He brought it over and we put it on my lift and looked it over. It was the same story, needed to be tuned. I drove it and it pulled pretty good until it cut out. I haven't heard from the owner in a while, but after reading your original thread, I emailed him a week or so ago to ask if he ever sorted out his car. I have not heard back but will let you know if I hear anything.
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Old 03-17-2017, 06:40 AM   #11
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The air temp is Bosch 0 280 130 085. I shall be ordering some shortly.
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Diagnostic testers for all models of Porsche 1987 >
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Old 03-17-2017, 06:56 AM   #12
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^^ does that temp sensor work in S4s as well?
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Old 03-17-2017, 07:01 AM   #13
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The air temp sensor in the engine air filter box is only used on 84-86 cars
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www.jdsporsche.com
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Old 03-17-2017, 07:03 AM   #14
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Installed in my '86 Euro....
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SharkTuned LH & EZ-F

www.jdsporsche.com
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Rebuilt LH, EZK ECUs & MAFs available from agents worldwide.
USA agent for LH and MAF checking and repair is Louie Ott :-
http://www.performance928.com
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Old 03-17-2017, 08:27 AM   #15
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^^ I guess the lh2.3 uses the knock sensors instead of this temp sensor to retard or advance timing. Thank you.
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