8 cylinder front engine iconic vehicle
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By Crumpler
#168817
Not sure why it’s not working, works from here, but try:

Fiveomotorsport.com

Option Porsche 928 MY 86 on drill down menu.
That should give you a couple of injector options.
Hope things are going well.
Dave
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By Crumpler
#170630
Big set back today.
I found out from Greg Brown that no SC 928’s could complete a lap on a race track. :(
Only his stroker motors can do that.
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By worf
#170636
Crumpler wrote: Sun Sep 11, 2022 3:30 pm Big set back today.
I found out from Greg Brown that no SC 928’s could complete a lap on a race track. :(
Only his stroker motors can do that.
This? On rennlist?
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By Hey_Allen
#170639
I thought his latest rant was that no euro 928 could survive a supercharger install?

Eh, I'm at the point that I'll seldom open a thread if his is the most recent post.


On the EFI topic, did you build your harness from scratch or did you pigtail off of the existing engine wiring to connect the VEMS?

I ask because I'm going to be going with a megasquirt 3X on my car and am debating the value of a from scratch harness...
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By Crumpler
#170645
That gem is found in the GTS v. Stroker thread.

Unfortunate that those on RL are only exposed to his narrative. But probably anybody who is serious about working/racing/modification of 928’s is, at least, knowledgeable enough to look at his posts with a degree of “scrutiny”.

I think that’s a fair way to say it right?;)

The harness: bought conversion kit, came with adapters and harness to VEMS plugs.
So stock harness except for top end stuff that I had replaced over the years.
Bulvot, briefly “Shifted” here, just did the megasquirt conversion and has alot of info up on RL.
He’s been tremendously helpful to me just keeping my sanity during the VEMS conversion, I’m sure would give you further insight with a PM. I believe he weighed pros and cons and decided to direct splice aftermarket ECU into stock harness.
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By grepin
#180981
Hi Dave,

I havent been doing much. In prep for my new injectors, which are not here yet, I stuck my old ECU and MAF back in. It starts and idles a lot better but is shit on the road. Old out of cal MAF I guess. I then plugged my VEMS back in with the original TPS in place. Back to rubbish starts but runs a lot nicer on the road. It went fine with the original TPS...from one drive. Plus its cal was in the correct direction. Also what laptop are you using and are you happy with it?

Greg
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By Crumpler
#181647
Ok, I was going to check on you soon :)

I am using some generic HP laptop, nothing special.

I haven’t done much either.
VE table mostly done.
I’m working in those higher MAP/RPM cells.
The 120 kPa is mid twelve AFR, 130 cells are still in the elevens.
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By Crumpler
#189215
Got it. Thanks.
Interesting and I’m grateful for the pin out info.
It’s still something I’m interested in doing.
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By Crumpler
#202460
Status: reasonable.
Got sidetracked with brake and tire upgrades.

Good performer, VE table ironed out.
Dipping my toe in the ignition advancement now.
I’m winging it. Maybe someone can speak to this.
Maybe I will post Peep’s initial timing map. I don’t know how close it was to stock mapping.
But his Boost cells have timing pulled.
My plan was to advance the cells where I need it , rather than the whole curve.
Which for me is mid-range to upper. I’m assuming normal for S3, but my power band traditionally feels like 3000-4500 rpm.
I have advanced cells in this rpm area, and cells up to about 2-3 pounds boost, not messing with bigger boost yet.
I have gone up a total of two degrees advancement in some of these cells, without knock events.
Pro tuning and dyno coming up in April to double check my work (and knock sensor data).
Sensor data looks real this far, but no data over 4000 rpm. I don’t have an area to do big runs around here without endangering civilians or going to jail.
I don’t think I would do well in jail.
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By maddog2020
#202464
Hey_Allen wrote: Sun Sep 11, 2022 4:15 pm On the EFI topic, did you build your harness from scratch or did you pigtail off of the existing engine wiring to connect the VEMS?

I ask because I'm going to be going with a megasquirt 3X on my car and am debating the value of a from scratch harness...
I've made several complete EFI harnesses on my 928. reach out to me if you have questions.
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By Crumpler
#219934
Updating thread. Final product.
For those that would find it at a later data.
Final dyno happened, numbers posted. Low boost 5-7 pounds.
I would have to say most time devoted was fabrication of tensioners in that limited space.
SC intake also a bugger. The S3 just isn’t a great candidate due to space, not to mention getting the top end to hold boost.
VEMS conversion huge upgrade to platform, but for a DIY without experience like me, you would want an ECU with active technical support.
It’s a different car and it would be hard to go back to a N/A 928, but I also wouldn’t do it again ;)

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By worf
#219942
Nice chart!
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By Crumpler
#219979
Thanks guys.
There’s probably more there but no knocks with the tune. AFR at wot low 12’s to high 11’s.
Engine is also tired. Last compression testing was ok but not awesome.

I also think this is the end point for the small blower pulley and the 6pk belt. Past 5000 rpm it still looks like some belt slip starting. Belt wrap and tension are at max, based on what I could pull off.

Assuming the DR twin screw has a cogged belt?
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By worf
#219988
Crumpler wrote: Sun Jun 11, 2023 7:42 pm Assuming the DR twin screw has a cogged belt?
It does not.
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By worf
#220182
Crumpler wrote: Mon Jun 12, 2023 10:55 am
worf wrote: Sun Jun 11, 2023 8:46 pm
Crumpler wrote: Sun Jun 11, 2023 7:42 pm Assuming the DR twin screw has a cogged belt?
It does not.
More then 6 ribs?
Same number of ribs as the alternator belt (since the extra-long SC belt also turns the alternator.)

5 IIRC. I've not counted them in a long time.

And no. No problems so far with slippage.
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By hans14914
#220507
Its a 6-rib pulley on the 928 Specialists kits. Oddly enough, there really isnt a lot of belt slip with the narrow pulley. I perpetuated the 6-rib myself on my designs, but I did replace the crank pulley and use a custom offset power steering pulley to bring everything backwards for hood clearance.

The factory crank pulley is sharper than the standard calls for, so it was causing some belts to shred. If you are using a factory crank pulley, it is advisable to take it to a shop to get it topped.
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By Crumpler
#220605
Good info, thanks.

I have a 2.85 pulley on the SC that was probably not helping, but reviewing logs last week it may not be slip. Boost stops increasing and flattens at 5000 rpm.
I don’t know if this is SC limitation (shouldn’t be), or leak, or intake restriction.

I also see trigger flags starting at 5000 rpm.
VEMS calls it decreased trigger signals. Causing small rpm artifacts.
That’s a damn rabbit hole I don’t want to go down but probably need to. My first track day is mid-July.

It doesn’t sound like the thread is final after all.
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By Crumpler
#220852
These are just notes for myself to maintain that crisp Lettuce feeling of emotional wellness. :barf:

In regards to trigger signal. The research I did was mostly about CPS spacing and non-ferrous flywheels causing issues. Which don’t really apply with stock set up.
Could be shielding with the old harness, I don’t know if that would be selective to a specific high rpm range? I could bypass run shielded cable to ecu to verify.
Could be VEMS. I found an old thread about 100-1 flywheels giving someone issues. I will try and consult with Peep if I can.
Hell maybe it is Porsche. Lol. Maybe it was within factory specs to throw an occasional trigger error at high rpm in 1986.

In regards to boost plateau. I assume the plateau also starting at 5000 rpm is unrelated to the trigger signal errors because it does not affect rpms.
I put the large cone filter back on and no difference with more surface area, so I feel I can rule out air restrictions.
I can’t completely rule out a boost leak opening at five pounds, but this is fishy because it achieves more than five pounds with intercooler off and more than five pounds in winter air.
So I’m starting to think the SC is maxed out. Which it really should not be per Procharger specs., but I just don’t know.
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By worf
#220870
Crumpler wrote: Thu Jun 15, 2023 9:33 pm I also see trigger flags starting at 5000 rpm.
VEMS calls it decreased trigger signals. Causing small rpm artifacts.
‘splain “trigger flags” / “ decreased trigger signals”

I think I know, but I want to be sure.
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By hans14914
#221086
I cant remember, does the VEMS have a trigger scope/logger? At higher speed, the voltage from a VR sensor can become very high. You may just have some over-voltage and the clipping of the signal could result in your loss of count.

I know a lot of computers allow for a RPM dependent filtering window. If the VEMS does, you may want to look at increasing this. Alternatively, you can use a resistor to dampen the signal to keep it below 5v.
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By Crumpler
#222264
I have a trigger log, but it’s all Greek to me :(
The tuner said blow it off unless it’s effecting engine actual, which I don’t believe it is.
Enough to effect log with artifacts.
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By hans14914
#222309
I cant see the scale settings on the trigger logs, its cut off in your photo.

It sure looks like you are saturating that input, and need to put a padding resistor in there to dampen the signal.

Hans
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By Crumpler
#222361
hans14914 wrote: Mon Jun 26, 2023 3:33 pm I cant see the scale settings on the trigger logs, its cut off in your photo.

It sure looks like you are saturating that input, and need to put a padding resistor in there to dampen the signal.

Hans
Ok, thank you Hans. I will look at that next.
Appreciate the info.
Dave
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By Crumpler
#224312
There is a VEMS dedicated thread on the other forum now. Trigger signal dropping at high rpm’s has been noted before. The cure for others was to use a non-Bosch CPS.
I was skeptical, when is 928 life ever that easy?

Installed a Facet model CPS (9.0212) and it worked like a charm. Can anyone expand on why?

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