Carpokes Porsche Forum

Hi All,

I've always done all my own work. Aside from a few very rare occasions where an expensive special tool was needed, no one else has ever been in my 951 aside from me, but I'm coming to the end of a very long and expensive surgery and I'm seriously considering taking the car in to a shop to have it 'finished'. Here's what I've just done (all of this started because I had an oil leak from the cam tower gasket):

1. Ported NA head with big valves from VPR
2. SFR Stage 2 headers and crossover, 3" downpipe, 'test pipe' (everything form the downpipe to the cat-back section)
3. RS Barn Stage 1 cam and adjustable cam gear
4. VEMS EMS

The car is running, but not well
- vacuum is low (around 12in/hg), and it's different with just about every start
- I burn the 'auto-tune' changes into the VEMS every time I drive it, but it feels like I'm starting from scratch each time 'cause it runs terrible until it gets a chance to tune some
- I definitely have a significant exhaust leak (pretty sure it's at the tie in form the wastegate dump - my factory one had been hacked up by a PO and so I had to make a new pipe and get 'creative' when tying it in to the SFR test pipe because I was in a hurry and only had 2 1/2" pipe on hand,
- I can't get the electronic boost control to work properly. I mean, VEMS thinks it's working, but I hit overboost protection every time I get into the boost
- the SFR test pipe hits the control arm mount pretty badly. I actually clearanced this some and somehow it got worse?!?

Basically, I've dumped a ton of money and time into this and I'm kind of afraid I'm going to destroy it while figuring out these last few things so I'm considering handing it over to the professionals to finish the job... But taking a car to a shop just feels weird to me - Looking for opinions. what do you think?

TIA!

Ultimately It will come down to whether or not there is a reputable and known shop/privateer in your area that knows the cars, and has exhibited mechanical and electrical skill in execution which I feel is key for the specific issues that the 944/951 can exhibit, particularly the 951.
There are outstanding and highly skilled people on this sight with a great wealth of knowledge and patience with questions that always seem willing to help. It depends on your tenacity in trouble shooting.

I think your issues probably fall into two categories. Things like exhaust leaks and exhaust pipes rubbing are fair game for any competent shop/mechanic. The bigger challenge is the VEMS in my opinion. Unless you find someone who is knows that system and how to get it working well on a 951, I think you're likely to be disappointed (paying endlessly for someone to tinker and figure it out, or paying for someone who just flounders with it). Getting any standalone set up to run smoothly in all conditions is an artform, and it "seems" like people who try the VEMs often struggle to get it set up without issues, before the basic tuning even starts.... @cda951 runs VEMs and may be willing to chip in -- and if you happen to be near Santa Barbara, I'd ask if he'd be interested in doing the work. He's one of the few people I can think of who know the car AND the ecu AND works on cars for a living....

ROB III wrote: Thu Aug 25, 2022 2:52 pm Ultimately It will come down to whether or not there is a reputable and known shop/privateer in your area that knows the cars, and has exhibited mechanical and electrical skill in execution which I feel is key for the specific issues that the 944/951 can exhibit, particularly the 951.
There are outstanding and highly skilled people on this sight with a great wealth of knowledge and patience with questions that always seem willing to help. It depends on your tenacity in trouble shooting.

Hi Rob, I'm fortunate enough to have a few competent shops in the area. They're booked out for a while though so that gives me an opportunity to do some work while waiting for their schedule to free up

Tom wrote: Thu Aug 25, 2022 3:21 pm I think your issues probably fall into two categories. Things like exhaust leaks and exhaust pipes rubbing are fair game for any competent shop/mechanic. The bigger challenge is the VEMS in my opinion. Unless you find someone who is knows that system and how to get it working well on a 951, I think you're likely to be disappointed (paying endlessly for someone to tinker and figure it out, or paying for someone who just flounders with it). Getting any standalone set up to run smoothly in all conditions is an artform, and it "seems" like people who try the VEMs often struggle to get it set up without issues, before the basic tuning even starts.... @cda951 runs VEMs and may be willing to chip in -- and if you happen to be near Santa Barbara, I'd ask if he'd be interested in doing the work. He's one of the few people I can think of who know the car AND the ecu AND works on cars for a living....

I am not in the Santa Barbara area, unfortunately - All the way up near Seattle There are some good shops here, though none I can find that specialize in VEMS. From what I can find on the internet, folks with VEMS typically fall into one of two categories - (1) Plugged it in, fired the car up, job done and (2) massive struggles the whole way. I, strangely, seem to be in a third camp where it does start and run, but I can't seem to get past it running "ok" and I'd really like it running great.

I'm vaguely in the greater Seattle area as well, and know-ish a fellow down in Tacoma who's been running VEMS for a year or so by now. Once mine's up and running that'll be another of us! I don't think he's got it fully dialed it, but it sounds like it's in much better shape than yours. Unfortunately I don't know if he has an account here yet, but I'll go bug him!

Silly question, and I don't really know how auto-tune works...but are you running it when the engine isn't fully up to temp? Figure it would converge on some parameters while the ideal set points are changing, and then run all funky in that case.

What's the AFR look like?

Echoing the others: I'd get all the exhaust leaks and such squared away before chasing mapping issues..and a shop can surely do that much. Out of curiosity, which shops did you hit up?

four0four wrote: Thu Aug 25, 2022 10:50 pm I'm vaguely in the greater Seattle area as well, and know-ish a fellow down in Tacoma who's been running VEMS for a year or so by now. Once mine's up and running that'll be another of us! I don't think he's got it fully dialed it, but it sounds like it's in much better shape than yours. Unfortunately I don't know if he has an account here yet, but I'll go bug him!

Silly question, and I don't really know how auto-tune works...but are you running it when the engine isn't fully up to temp? Figure it would converge on some parameters while the ideal set points are changing, and then run all funky in that case.

What's the AFR look like?

Echoing the others: I'd get all the exhaust leaks and such squared away before chasing mapping issues..and a shop can surely do that much. Out of curiosity, which shops did you hit up?

It's great to hear there's another couple 951s with VEMS in the area! I'd definitely love to pick the brain of this guy in Tacoma who's got his working well also if you can put us in touch.

I read through your thread - are you close to tuning time yet?

VEMS doesn't speak AFR, only Lambda and that just "means" a lot less to me than AFR so I'm struggling to remember numbers but I do recall being a little lean under boost - in the 12.5:1 range. I'd like to be closer to 11.5:1

Regarding auto tune, I'm not sure I quite understand yet how it works either but I do know that it doesn't work at all until coolant is over 70C, so it's basically useless to tune startup and warmup curves.

The only shop I've talked to so far is Group 2 in Woodinville. But they seemed pretty booked out. There's a pretty well-regarded tuner in Monroe that I may talk to about the VEMS but I'll still need to sort out all the other issues first.

Where in 'vaguely Seattle' are you? I'm up in Snohomish County, east of Monroe.

Sorry, busy times...

crackership wrote: Fri Aug 26, 2022 10:16 am

It's great to hear there's another couple 951s with VEMS in the area! I'd definitely love to pick the brain of this guy in Tacoma who's got his working well also if you can put us in touch.

I need to pick up some parts from him, so I'll ask!

I read through your thread - are you close to tuning time yet?

Not remotely

VEMS doesn't speak AFR, only Lambda and that just "means" a lot less to me than AFR so I'm struggling to remember numbers but I do recall being a little lean under boost - in the 12.5:1 range. I'd like to be closer to 11.5:1

Regarding auto tune, I'm not sure I quite understand yet how it works either but I do know that it doesn't work at all until coolant is over 70C, so it's basically useless to tune startup and warmup curves.

afaict "lambda" is just uncorrected for fuel characteristics (so, correlated 1:1 with AFR less some scaling factor).

The only shop I've talked to so far is Group 2 in Woodinville. But they seemed pretty booked out. There's a pretty well-regarded tuner in Monroe that I may talk to about the VEMS but I'll still need to sort out all the other issues first.

Where in 'vaguely Seattle' are you? I'm up in Snohomish County, east of Monroe.

Group 2 is great! They used to have a cool spot in the city, but moved out a year or so back. There's a handful of Porsche specific shops that enjoy good reputations. In my experience they're usually happy to tell you what shops they use and/or refer people to for various jobs. Aker's, Chris', Dobson, to name a few.

I'm vaguely in Seattle, the city

" I definitely have a significant exhaust leak (pretty sure it's at the tie in form the wastegate dump - my factory one had been hacked up by a PO and so I had to make a new pipe and get 'creative' when tying it in to the SFR test pipe because I was in a hurry and only had 2 1/2" pipe on hand,"

This is a concern. At idle the exhaust pulses can draw in raw air into the crossover pipe which will trick the O2 sensor into thinking it's leaner than it actually is. In other words, you'll see a false lean AFR. This will def cause problems with the VEMS autotune. Typically, an exhaust leak before the O2 sensor will cause more false-lean readings at idle but will show true AFR's as the throttle opens more and exhaust volume increases.

Most good tuner shops will also verify that the engine/turbo/fuel systems are in good working condition since a problem in these areas will throw off the tune. From my experience, mechanical issues need to be sorted before the car goes on the dyno for tuning. For example, if you didn't time the cam correctly when you installed the head, you'll get low idle vac, a lumpy idle or other issues that are not related to the tune. It can be tricky to differentiate mechanical issues from true tuning issues.