Vitesse STEALTH MAF/MAP Kit

[Fast951]

I was able to manipulate the MAF tube a little but still couldn’t keep one side from making contact with the coolant manifold. So, I cut a short section of Rennline fuel line and cut it lengthwise to put between the coolant pipe and the MAF sensor housing.

Ideally you do not want the MAF to touch the coolant pipe. Vibrations and heat are not good! I would add some sort of a heat barrier (Amazon has them) to protect from heat.

What condition are your engine mounts?

[michael2e]

Very interesting reading about the idling issues with your S. I also have a 951 and an S2. Been having a devil of a time sorting out similar issues in the S2 that you seem to have experienced. Initially my idle instability seemed to be classic ISV improperly functioning. The previous Bosch ISV I put in 10 years ago had worked perfectly until fairly recently so I also decided to go aftermarket and use one of Ians (944online) due to the high cost of OEM. He sells Chinese units that he swears have worked for all of his customers. He's never had a return on one allegedly. After install my car now starts, idles and drives perfectly but soon after will intermittently idle at over 2k with wild rpm swings as the TPS idle feedback loop tries to knock her down to normal. Then by the next stoplight she's purring like a kitten again. And on&off all day like that. Just like you - everything (AFM,TPS,FPR, DME Temp sensor, vacuum) tests normal but I still get intermittent crazy fast idle. I thought perhaps this new ISV was faulty so Ian swapped it under warranty for another one which is doing the same thing. Unplugging the ISV or clamping its inlet hose settles the idle perfectly. I've considered just running without it but the cold starts are rough. Besides. So I've started thinking also that maybe these aftermarket ISVs just aren't compatible with the S/S2? I've used them (3 pin) with the 951 which idles perfectly. Anybody else have issues like this? Or am I missing something? Cheers!

[NCGermerican]

It appears that you have a 2.5bar FPR. The software is configured for a 3bar FPR.
The difference between the 2.5bar and 3bar FP is about 9% flow. To get by while waiting on the 3bar FPR, set the FQS to +10% fuel (refer to the supplied FQS document).

FYI AFRs during the cold start should be in the 11s or even richer if cold. Then as the engine warms up, AFRs will lean out and will start closed loop around 14.7:1.

Thanks John - I actually got the new FPR last night and installed it. It turns out it has the EXACT same readings as my other one. I did some research and come to find out the 3.0 FPR should read 3 bar with NO vacuum. I pulled the vacuum line while running and it immediately went to 3.0. So, it looks like the FPR isn't the issue. I'm going to try to take a video tonight and log on my F9 DME from a cold start and then again on a warm start.

[NCGermerican]

Very interesting reading about the idling issues with your S. I also have a 951 and an S2. Been having a devil of a time sorting out similar issues in the S2 that you seem to have experienced. Initially my idle instability seemed to be classic ISV improperly functioning. The previous Bosch ISV I put in 10 years ago had worked perfectly until fairly recently so I also decided to go aftermarket and use one of Ians (944online) due to the high cost of OEM. He sells Chinese units that he swears have worked for all of his customers. He's never had a return on one allegedly. After install my car now starts, idles and drives perfectly but soon after will intermittently idle at over 2k with wild rpm swings as the TPS idle feedback loop tries to knock her down to normal. Then by the next stoplight she's purring like a kitten again. And on&off all day like that. Just like you - everything (AFM,TPS,FPR, DME Temp sensor, vacuum) tests normal but I still get intermittent crazy fast idle. I thought perhaps this new ISV was faulty so Ian swapped it under warranty for another one which is doing the same thing. Unplugging the ISV or clamping its inlet hose settles the idle perfectly. I've considered just running without it but the cold starts are rough. Besides. So I've started thinking also that maybe these aftermarket ISVs just aren't compatible with the S/S2? I've used them (3 pin) with the 951 which idles perfectly. Anybody else have issues like this? Or am I missing something? Cheers!

I'm not an expert on this, but I believe the 16v cars rely much more heavily on the ICV than the 8v cars, mainly because there is NO idle adjustment on the TB. Therefore, they can be much more "finicky" and if resistance readings are not perfect, you end up with intermittent idle issues. Like I said in my post - it was night and day once I put in the Bosch ICV. I know they are pricey (and now VERY scarce), but it's worth it to not have to keep ripping my hair out trying to figure out what's wrong.

[michael2e]

Well NC I really have to thank you for confirming my thought that the aftermarket ISV was potentially the culprit. After "ripping my hair out" going back nearly a year chasing the fast erratic idle I decided to clean up my old Bosch ISV and stick it back in. Man, just like you everything settled down to normal and the idle is perfect. I think you're absolutely right that the S/S2s may be more finicky when it comes to the ISV functions compared to the 951s. I tried not one but 2 aftermarket ISVs and they both behaved erratically from the start. Changing out the most recent one I was surprised that the internals were banging around when I shook the thing! well you get what you pay for I guess...but what a waste. Not to mention the wasted hours of testing everything else. I should probably do a write up for the main 944 forum. Cheers!

[NCGermerican]

I was able to manipulate the MAF tube a little but still couldn’t keep one side from making contact with the coolant manifold. So, I cut a short section of Rennline fuel line and cut it lengthwise to put between the coolant pipe and the MAF sensor housing.

Ideally you do not want the MAF to touch the coolant pipe. Vibrations and heat are not good! I would add some sort of a heat barrier (Amazon has them) to protect from heat.

What condition are your engine mounts?

Thanks John - I've gotten it positioned that it's barely touching. I tried to move it every way I could and still have the hood close. I was able to insulate the hard pipe with some fuel line- I tried some silicone line but the walls were too thick and I couldn't get the airbox low enough on the mounts to close the hood. My motor mounts are brand new Porsche - I installed them a few months ago when I put in the Evergreen Raptor.

[NCGermerican]

Well NC I really have to thank you for confirming my thought that the aftermarket ISV was potentially the culprit. After "ripping my hair out" going back nearly a year chasing the fast erratic idle I decided to clean up my old Bosch ISV and stick it back in. Man, just like you everything settled down to normal and the idle is perfect. I think you're absolutely right that the S/S2s may be more finicky when it comes to the ISV functions compared to the 951s. I tried not one but 2 aftermarket ISVs and they both behaved erratically from the start. Changing out the most recent one I was surprised that the internals were banging around when I shook the thing! well you get what you pay for I guess...but what a waste. Not to mention the wasted hours of testing everything else. I should probably do a write up for the main 944 forum. Cheers!

Glad to hear it worked, but sorry to hear about all the wasted time and money - I was right there with you. In fact, I'm now convinced that was the issue all along and make me abandon my S2 intake system swap on my S. I ended up going back to stock and sold all of my S2 intake bits - talk about wasting time and money!

[[email protected]]

Hey Folks. I'm currently installing the Vitesse Stealth MAF/MAP kit on my 87 951. I went with the stealth kit because this will be more of a show car than a go car, so I prefer to keep the look of the factory airbox....especially since I paid over $400 for a brand new one earlier this year.

So far I have hit a snag with the fitment of the aluminum pipe with the MAF (that replaces the AFM). Per the supplied instructions/pictures, the MAF sensor plug should be mounted upside down with the plug side slightly rotated towards the front of the car. The problem I'm running into is that it's touching the coolant manifold bar and because of this, the factory airbox won't sit all the way down in it's mounts. Therefore, my hood won't close (my brand new hood insulation seems to be pretty thick).

I'm wondering if anyone else has installed the stealth kit, and if so, could you chime in with any tips and tricks? If not, my next step is to fabricate a new MAF tube so I can move the placement of the MAF in BETWEEN the factory airbox and the intercooler to throttle body pipe instead of UNDER the IC to TB pipe. This probably sounds confusing and I'll try to take some pics later tonight.

Where did you get the stealth version of Vitesse MAF?
I have a non stealth but would rather have the stealth

[NCGermerican]

Where did you get the stealth version of Vitesse MAF?
I have a non stealth but would rather have the stealth

I ordered it directly from @Fast951 (John) at Vitesse. I don't know if the actual MAF sensors are different between the two setups, but you can reach out to him and ask what your options are. He may be able to sell you the MAF tube - it's a cusotm C&C machined piece of aluminum that is mounted on the tube that the MAF attaches to.

[[email protected]]

Where did you get the stealth version of Vitesse MAF?
I have a non stealth but would rather have the stealth

I ordered it directly from @Fast951 (John) at Vitesse. I don't know if the actual MAF sensors are different between the two setups, but you can reach out to him and ask what your options are. He may be able to sell you the MAF tube - it's a cusotm C&C machined piece of aluminum that is mounted on the tube that the MAF attaches to.

When did you purchase it?