924Board.org

[Nein37]

Took a peek today at my spark plugs just to check if there was any detonation damage. As soon as I took the IC off I noticed that the boost line that was SUPPOSED to be hooked up to the WUR was plugged instead and unhooked! At some point during my troubleshooting this past fall I had unhooked and plugged it. I was sure I had reconnected it but... instead I get the moron award. User error!

So I hook her back up, check the plugs which all look fine, take her for a ride and low and behold... AFRs down in the low 11s on boost. She handles 14psi just fine without pinging. Woot!

Sorry for the wild goose chase but at least Grenadiers solved his glowing manifold problem.


I recently installed a wideband and have found that my car needs to be tuned very rich to avoid pinging on boost. I started at a (stoich) of 14.7 at idle, this was definitely too lean but I wanted to get an idea of what kind of enrichment I'd see. Then I lowered it to 13.5 still pinging, then I went down to 12.5, still pinged. At all tunes the enrichment only went to 12.5. I've changed the boost around during the tuning between (11-14lbs) and found it seems to have little effect with respect to the pinging. I'm just not getting good enrichment on WOT, hovers around 12.5 which is WAY to lean and sometimes seems to be rising instead of getting lower.

I've richened the tune now and currently have the car idling at 11.5 A/F. This is about the value you get when adjusting the mixture halfway between engine stumbles, then giving it an additional 10 degree turn to lean, to compensate for the extra air entering around the wrench. We'll see how this goes tomorrow.

Ideally I'd liked to be tuned to about 12.5 at idle and was hoping WOT enrichment would get me to around 11 at WOT. This is not happening.

I've added an extra shim to my primary pressure regulator in case my system pressure is a bit low.

Boost hose is hooked up to the WUR, which is recently rebuilt. I wonder if an adjustable WUR would do the trick for me?

I'm also wondering if my throttle position switches are on the fritz. I assume the TPS talks to the Lambda system to let it know what to do with respect to the frequency valve but I just don't feel like my enrichment system is working very well.

I'm currently running closed loop (unplugged OXS) but I should still see enrichment at WOT I assume?

I plan on programming the 2nd analog output on my wideband to simulate the OEM OXS signal (really would like the fuel economy this system provides, although it runs fine in closed loop). What values does the OXS bounce between? 0V-5V or 0V-1V?
_________________
1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

[Rasta Monsta]

The unanswered question is, WHY is the car pinging on boost.

Does it have a fuel delivery problem? This includes fuel system volume (pump/filter) AND factory boost enrichment (WUR functioning properly?).

Is the "on boost timing retard" function working properly?
_________________
Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[Nein37]

I'll have a better idea after tomorrow. With the car currently idling at 11.5 A/F I'll see where the full load enrichment lies.

The pinging occurs with a full load A/F of 12.5 to 13. I believe this would be normal behavior for boost levels of 12-14 lbs. Just not enough fuel. I'm hoping with the richer tune I'll get to the WOT enrichment values needed to avoid ping.

I'll also check my system pressure again and my WUR function but the whole fuel system has been gone through this past year and all was good.

Not sure how I'd go about checking whether the DITC was properly retarding timing or not???
_________________
1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

[Cedric]

[stevekat]

John, keep in mind U.S. cars run stock at ~7 psi without CGT intercooler. Not sure where you should get with the CGT intercooler, but 14 psi would be a 100% increase. I get to about 10 - 10.5 psi with CGT intercooler, digital WUR and Euro DITC, and I notice as the weather gets warmer, I probably need to back down a bit.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[ideola]

Steve, just to clarify, that's with essentially with the out-of-the-box map from Unwired Tools, right? I think I recall reading that you hadn't yet gotten around to playing with the maps to see what could be done from an enrichment perspective?
_________________
erstwhile owner of just about every 924 variant ever made

[stevekat]

Correct, that is with an out of the box map, that they created for their Series 1 924 Turbo.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[ideola]

[stevekat]

Besides the adjustability, it is nice to be able to plug in at anytime to confirm the WUR is operating correctly, or at all, for that matter.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[Nein37]

Some testing today. At 11psi the ping is gone and my AFR gets down to around 12. I think the reality is that the stock enrichment setup isn't up to the task of fueling anymore boost. As Steve said.

The only other possibility would be a malfunctioning frequency valve that is not providing enrichment at WOT. I'm running open loop without the OXS hooked up but as I understand the computer should go to full enrichment when the throttle switch indicates WOT. I'm gonna look into this as a possible cause.

If that checks out then I think the only 2 options are either an adjustable WUR or the Unwired Tools digital WUR. While the digital WUR is certainly the more flexible of the 2 I'd rather just get the OEM WUR modified to increase enrichment on boost. I'll have to comb through the 930 boards at Pelican to find out the details on this option.

Steve,
Is this a new map they created or are you still running the 3 bar constant? I'm also interested to know what the limit of the CIS system is with the digital WUR. As long as the fuel is there I just don't see an issue with running these engines, intercooled of course, at 15psi. If the digital WUR can keep you down at 11 AFR all should be good.
_________________
1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

[ideola]

If you do a search on brian leask, you'll find some of the details on his adjustable wur right here. I'm mobile at the moment, so somewhat technology-impaired, otherwise would post link...
_________________
erstwhile owner of just about every 924 variant ever made

[stevekat]

My narrow band gauge reads rich at high rpm/high boost, even when I dial up boost to the extent I get pinging. Just having a rich mixture, I believe, does not assure lack of pinging. Otherwise intercoolers would not be necessary, just fuel. I think the algorithm is more complex...pressure, charge temp, mixture, ignition timing, octane, etc.

In colder weather, with U.S. DITC, I think I've gotten up to 13 or 14 psi, but that was in very cold weather. I was just at the car this last weekend, and with Euro DITC, had to reduce boost to about 10 psi or perhaps a tad less. As things get warmer, and air less dense, ability to boost might decrease. So the numbers you're getting *may* be about right.

My control pressure on the UTCIS is not constant. Under boost it varies from 3.5 (low boost) to 4.1 (at higher boost.) On the UTCIS, boost is considered above 1.0 bar (with one bar being sea level.)
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[Nein37]

I am being hopeful since the timing isn't something that's adjustable. I imagine the efficiency of the stock turbo isn't helping, by 12psi it's probably starting to pump a bit too much heat.

Ok so the factors that are changable:

1. Turbo: The problem is I like the early response of the smaller stock unit so going bigger isn't really something I'd want to do.

2. Intercooling: Gosh darnit... I have a CTG intercooler, I want to get the most I can from it. Of course, with the D9 GTS lights and the washer tank delete I have plenty of room in the passenger front corner to add an additional cooler. (I'm seriously considering this option)

3. Fueling: Current enrichment seems to bottom out at around 12 to 12.5 AFR... these numbers just don't support higher boost levels. When I get my WOT enrichment numbers down to 11 AFR I'm hopeful that will be able to bump up boost a couple psi.
_________________
1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

[flosho]

Personally, I'd either stick with the CGT cooler or go all out and put an intercooler in the front, and NOT behind the head light.

The big problem is people want 2.5-3" piping and it doesn't need to be more than 2.25" which can tighten things up and still flow plenty of air for our cars.
_________________
[This Space For Rent]

[stevekat]

The CGT top mount intercooler is probably less efficient than many - due to size and position. But it is a beautiful unit, and fits the car well. Rather than hack things up, I'd just go with the clean OEM CGT set up and stay true to form. If one wants more and more power, the 951 is clearly what to opt for...but to keep with the classic 924 derivative, the CGT iteration is clean, original and quite unique. Also, the CGT intercooler, boosted to maximum safe pressure, whatever that may be, is a very fun, spritely car. I have some very fast, powerful cars, but the 931 puts a smile on. For mine, I am not trying to be faster than everyone, just maximize performance based on keeping things relatively original (and reliable.) For me, opting in to updated technology (digital WUR) and probably a wide band AFR is around where I want to be. I want the stock air box. I'd go with any factory turbo (Series 1, Series 2 or CGT) for the car, but don't want to modify beyond bolt in, in that department. I'd use any stock wheel found on the car...Fuchs as on the CGT, flat dish (but would not have any problem using the wider 7's and 8's from the 928, because they are the same form of wheel.) For me, the fun and joy is to keep things as stock as possible (or OEM) while incrementally pushing performance using original concepts and systems, Part of the idea is to enjoy the classic stock nature of the car, within its factory street interations. The other direction is to go for power and upgrades. The two are somewhat incompatible past just modest upgrades. Also, if one wants power, our platform is a poor starting point. The 951 is a no brainer in this department. When doing modifications on any of my cars, I've always regretted straying far from factory configuration - the process is fun, but the result wears off quickly, and I've always yearned to go back and be closer to what rolled out of the factory. This may just be me.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.