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Quote:
Originally Posted by patkeefe View Post
72 PSI is spec for an SC head, which I think is all I can get from the SC pump. At 72, I just about run out of fuel at high RPM, according to the dyno sheeets. So, I have too much in mid range, and barely enough at top end, hence the consideration of series sequential pumps. I'm just trying to figure out how to turn the second pump on.
Pat
Pat, a Bosch 044 motorsport fuel pump might be an option. Cheaper than most stock pumps (I paid $200 US for a brand new one) and the specs are much better than anything the factory fitted.

Bosch are very conservatively rating this pump too - I've seen people claim it out-flows the Walbro "300 l/p/h" pump and makes higher pressure doing it, even though the official spec on it is only 200 l/p/h according to Bosch. Stock fitment on 500HP Cosworths.

That's all I have - my only fuel pump, fitted in the stock front location - and my system pressure doesn't twitch under full boost.

I also tend towards taking off the RPM solenoid and tuning the WUR. Mine was fitted (but not plumbed) for the dyno runs - turns out it wasn't needed, did everything on the WUR. Took it off in the end.

What boost pressure trigger did Brian Leaske set your WUR for? IIRC, mine came set for 6 or 7 PSI - which wouldn't even trigger on your car, @ 5...


Have you asked Stephen if the IA-modified head is non-linear in the mid-range? That seems odd, if the classic CIS tuning problem seems to be a pig-rich mid-range to keep the top safe - so, if anything, I'd have thought they'd have made the top range pig rich and left the middle alone (or just slightly fatter)? But obviously he'd know for sure.

HTH.
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'77 S with '78 930 power and a few other things.
Old 01-03-2008, 07:32 AM
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spuggy:
the RPM Solenoid really doesn't come into play at the moment. I'm hitting this little flat spot wall at about 3500 RPM, and the RPM switch has a 4600 RPM module in it, so I am not sending any boost pressure to the WUR. I believe it's set to 5 PSI, which then drops control pressure to maybe 2.3 bar, but I have to put the mighty-vac and gauge back on it to verify...Brian may have reset it.

On the 930 WUR, how are the boost/vacuum connections made? I have boost pressure on the horizontal tube, and the top, vertical tube is open to atmosphere on my WUR.

Pat
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Old 01-03-2008, 09:37 AM
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Oh, yeah, one more thing...
this pig rich mid range problem existed before I blew up the old plastic airbox, which is why I spoke with BL and decided to get the RPM Solenoid switch, which worked pretty well. After installng the RPM Solenoid switch, the car was driveable, and it worked OK at the track. The flat spot has existed since I changed the airbox to the lower profile stainless steel unit. I suppose I may have altered the characteristics of how the plate (and plunger) lifts by changing the airbox. Maybe more air tries to flow up on one side of the plate, so I get the same volume of air, but it is actually traveling a path across less of the plate, so it moves faster and pushes up the plate more. Kind of analagous to same total pressure in a duct, but more dynamic pressure and less static pressure.
Pat
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Old 01-03-2008, 11:29 AM
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Quote:
Originally Posted by patkeefe View Post
I'm hitting this little flat spot wall at about 3500 RPM, and the RPM switch has a 4600 RPM module in it, so I am not sending any boost pressure to the WUR.
I'm still conceptually struggling with this. I can't see that the fuel head would be as massively non-linear as it appears to be - and yet your mixtures are good in N/A mode lower down, and the RPM solenoid should be stopping you getting any boost enrichment at all.

Given the symptoms, I'd try routing the vacuum line straight past the RPM solenoid and into the WUR and see a run to see if it's any different? I know it doesn't make sense, and yet...

In your position, I think I'd also be inclined to talk to IA, or shim the regulator in your SC fuel head to something approaching 930 specs 6.0-6.7 bar (88-98 PSI) and try that.

Quote:
Originally Posted by patkeefe View Post
On the 930 WUR, how are the boost/vacuum connections made? I have boost pressure on the horizontal tube, and the top, vertical tube is open to atmosphere on my WUR.
That sounds right (and looks like it agrees with the vacuum diagram), but I can't go outside and look at my car right now.
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Old 01-03-2008, 11:34 AM
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Quote:
Originally Posted by patkeefe View Post
I think my AEM has the wiring for connecting up an RS-232, such that I can probably log some data on my laptop via hyperterminal. I'll have to look into this, as what you say is a pretty good idea. I generally just memorize readings and RPM readings, but my feeble mind does not have the storage capacity of a disk drive.

Pat

Yes the AEM UGEO widebands have an R232 data feed that can be patched into a serial port line for datalogging. Blue 20awg from the four wire harness. Just need to run that wire and a ground wire to the proper pins on a serial adapter(can't remember those locations, but they're in the instruction manual) I've messed with more than a handful of the AEM counterparts here. So so results....

However, you really should get an LM-1. While the AEM's do react fast, are pretty cost effective, and for the most part let you know what's going on they are not anywhere near as accurate as an LM-1. I've logged AEM plots while street tuning some cars here, and then once up on a dyno for the final pulls and an the shops LM-1 logging away I've recorded variances in the AEM sensors from .2 as much as 1.18!! I double checked these discrepancies by checking subsequent pulls using my own LM-1 which I bring to all dyno pulls with customers car incase it's ever needed.

I point fault in the AEM units to the calibration resistors in the main sensor connector. None ever seem to be dead on....
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Old 01-03-2008, 06:22 PM
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FYI, i use a single Bosch 44 pump in my car, I see 100+psi on my fuel pressure gauge.

I have a LC-1 W/B and A/F gauge in my car which can be output to a PC and used like the LM-1 unit.
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Old 01-03-2008, 06:32 PM
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After a little research on the pinout of the 9 pin RS-232 connector, I have deduced I can't get multiple inputs, such as AFR and RPM without a device, such as an LM-1. So much for cheaping out on that!

Here is where the AFR's were on the dyno, prior to the install of the RPM solenoid switch. Boost for this test was at about 6 PSI, not 7.5 as noted.
And, I will over the weekend check to make sure my blowoff valve is closed down under boost, and not cracking open. I hope the fix is so easy. We had some of that Minn weather here the past few days...

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Old 01-04-2008, 03:52 AM
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Hmm...you don't happend to have boost curve as well? I guess curve marked "power" (piking curve) is actually torque curve and the thick curve is power curve?

The sheer look of your torque curve indicate a substantial boost spike. Your wastegate might be binding and all that excess boost is vented trough you pop-off valve.

1. Check wastegate for binding, grease it up if needed.
2. Close pop-off valve shut.
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Old 01-04-2008, 07:53 AM
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Goran:
I have the curves in another thread, which I will try to find in this forum. That thread is: BAE Install Dyno Data

I have since changed the old wastegate to a new Tial Sport with 5.8 PSI spring.
The pop off valve is actually a return valve back to the inlet side of the turbo, vacuum controlled. I believe it is an OEM Audi valve. I believe you have a good idea about that, maybe I am bleeding of boost, so I will plug it this weekend and see if I get any improvement with it plugged.

Pat
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Last edited by patkeefe; 01-04-2008 at 10:42 AM..
Old 01-04-2008, 10:37 AM
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Quote:
Originally Posted by patkeefe View Post
Goran:
I have the curves in another thread, which I will try to find in this forum. That thread is: BAE Install Dyno Data

I have since changed the old wastegate to a new Tial Sport with 5.8 PSI spring.
The pop off valve is actually a return valve back to the inlet side of the turbo, vacuum controlled. I believe it is an OEM Audi valve. I believe you have a good idea about that, maybe I am bleeding of boost, so I will plug it this weekend and see if I get any improvement with it plugged.

Pat
No, I'm talking about pop-off, not BOV. I'm talking about rectangular spring-loaded thing on the top of your air-box:


I assumed that your home-made sping-loaded pop-off valve was downstream from turbo. Your picture makes it somewhat hard to understand the path of air. What I was trying to say is following:

1. Boost momentarily spikes above normal due to unknown condition.
2. Spring-loaded thing opens due to excessive boost, dumping measured air.
3. CIS still believes that dumpad air is in the loop and injects extra fuel and rich condition occurs.

I understand that there is BOV in the loop as well, but as BOV (hopefully) re-circulates air back into turbo intake it will not affect AFR condition as it keeps air in the loop and is only open during the shifts.

With other words, keep an eye on everyting that might vent air during the boost onset. Especially the spring-loaded thingie (if it's in pressurized part of air) and eventual cracks.

Also, your boost treshold is waaay high up in revs. You either have a monster turbo or a gigantic leak somewhere.
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Old 01-04-2008, 02:18 PM
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I agree with Goran, your pop-off valve may be the culprit. While that valve is invaluable for an SC it is a potential leak for a 930.
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Old 01-04-2008, 05:44 PM
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I hope the fix is that easy. However, the original dyno tests were done with the old SC airbox, with a plumbers plug on the popoff valve. That's why the airbox blew up.

But, agreed, the logic of leaks after the air has been metered makes a lot of sense. It's on the list of stuff for Saturday.
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Old 01-04-2008, 06:06 PM
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Goran and Brian:
You guys are wizzards! I siliconed the gasket and plate, and bolted the popoff plate down hard. Car now has zero transition problems! The AFR sems quite more linear wrt RPM, doesn't drop to the wretched 10 AFR; actually just makes it into the 11's range on AFR. The difference is unvelievable. Boost gets to 6 PSI, and holds, doesn't drop off at all. Everything seems to work like it was supposed to.

So, looking back, I can now guess that my plastic airbox must have leaked all along. The car has never run this strong since I built it. I will further guess the big spike in the original dyno curves are gone. I'll know when it goes back on the dyno.

So, all I need now is to tweak the WUR a bit, and get it a tad bit richer at low to mid range RPM.

Thanks! You guys rock!
Pat
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Old 01-05-2008, 08:45 AM
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Pat, I have spoken to the maker of the SS box in the past, they used different springs to hold the plate down just for turbo applications, I believe they were nothing more than brake shoe springs but he did say they used ones with different tensions to hold the plate down for boost but still allow it to open for backfires, I used the plumbers plug with my plastic box also, but never had it backfire.
The SS box should also improve the performance off boost as it flows better than the original.
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Old 01-05-2008, 10:03 AM
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Good deal.
Please report back when you dial in the WUR. I am interested to see if your WUR has enough adjustablility, when combined with the big fuel head, to eleminate the RPM switch.
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Old 01-05-2008, 10:28 AM
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Chappy:
Yes, I have some stiffer springs. Now that I have the cause of he problem identified, I will try out the other springs. I do like having the popoff functionality.
Rarlyl8, the weather is supposed to be ok this week, so I can use the car some. I'll see how the WUR/RPM solenoid work out and report back.
Pat
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Old 01-05-2008, 01:06 PM
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Pop-off valve should be deleted alltogether. The very reason for backfire is probably the overrich condition caused by pop-off valve that is there to cure it. Turbocharged engines have very long airpath between inectors and airbox (containing turbo inbetween) that backfire is very unlikely if AFR's are OK.

You should pressure-test whole assembly the way I tipped Alan about. Pressurize it to whatever boost you are running +4 PSI and make sure nothing leaks. These engines are full of leaks.

Also, a little intercooler wouldn't hurt either.

If you fancy experimenting, you can fuel it with E85, lower the control pressure until you reach same AFR, up the boost a bit more and run more agressive ignition timing.
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Old 01-05-2008, 01:18 PM
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There will be a point when you will do as i did and replace the old SC SS air box with a 930 intake.
But i will say the SC box worked for me. The 930 intake fits better in the 914 but the SC has the large intake runners.
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Old 01-05-2008, 04:23 PM
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Quote:
Originally Posted by beepbeep View Post
Pop-off valve should be deleted alltogether. The very reason for backfire is probably the overrich condition caused by pop-off valve that is there to cure it. Turbocharged engines have very long airpath between inectors and airbox (containing turbo inbetween) that backfire is very unlikely if AFR's are OK.
Goran, there is actually a very short path from the intake valve to the airbox. There would be a longer path for the pressure wave to dissipate, but the throttle butterfly,when closed, is basically a closed valve, which won't allow any pressure wave past it. Hovever, I buy into your theory of the necessity of the valve, although it only takes one deviation from theory to blow the airbox up.

Quote:
Originally Posted by beepbeep View Post
You should pressure-test whole assembly the way I tipped Alan about. Pressurize it to whatever boost you are running +4 PSI and make sure nothing leaks. These engines are full of leaks.
I agree with this, and will figure out a way to do this, using your previous post as a reference.

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Originally Posted by beepbeep View Post
Also, a little intercooler wouldn't hurt either.
I have a water injection system; comes on at whatever boost level I set it to. I have different size nozzles which I can use. Right now, I have a 2 GPH nozzle installed. I try to use the smallest nozzle which allows complete vaporization of he water. I have instrumentation to look at the air temps inside the airbox, so I can see the temperatures after the compressor and nozzle. For example, at the track, where I can basically be on boost all the time, I can get temperatures approaching whatever ambient I have going into the air filter (I have a temerature gauge there also). I believe this setup is as effective as an air-air intercooler. I do not want a tail on the car. I prefer "looks slow, goes fast". And, water is a good anti-detonant, especially when mixed with alcohol.

Pat
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Last edited by patkeefe; 01-06-2008 at 05:55 AM..
Old 01-06-2008, 05:52 AM
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930 never ever had pop-off valves and never suffered from backfire. If they did, you couldn't hear it or intake assembly was much stronger than SC's and thus didn't blow.

As far as I understand, your car is somewhat special case where you have something you call "airbox" which is actually nothing but home-made plenum chamber. For me, "airbox" is assembly containing filter and is situated before CIS and turbocharger. Most factory turbocharged cars have very stong cast "plenum chambers" (=cavities between throttle and heads) and thus are immune to backfire. Yours seems to be built of rectanglular steel sheets?

Typically, if a turbocharged plenum cannot survive occasional "burp", it shouldn't be used on a turbocarged car Also, backfires occur when fuel is poured into stacks w/o any spark to ignite it and shouldn't happend at all.

Anyway, I'm glad that you found the culprit! I still find your boost treshold amazingly high up the revs. Is it some sort of old Ray-Jay turbo you are using? I believe you can make your engine respond much much better if you find the reason of late boost buildup. Is turbo too big? Maybe you have a leak somewhere? Frankly, for your power level a KKK K26 (Audi 200 Turbo, Porsche 944 Turbo) would be a perfect solution! They are plentiful and not expensive.

Regarding water injection: well, it's a working solution but frankly...it should be regarded as band-aid. It would be pity to destroy the engine if water runs out or the pump stops working Some people have built neat little intercoolers that fit under the duck-wing. Take a look at OEM intercooler from SAAB 900 <92. It's quite compact...you might be able to install it. Also, if you are handy you could make water/air system. They are very compact and effective albeit somewhat complicated.

I'm looking forward to seeing AFR and power curves. 250hp from your combo on 6 psi boost is very good! OEM ROW 3.0 930 made 260hp with 0.8 bar. A more responsive turbo and a touch more boost and you will have very driveable and peppy car indeed!

P.S. Personally, I don't think yo should run AFR's richer than 12.2 when on boost. There is mileage and power to be made there.
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Old 01-06-2008, 06:52 AM
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