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This is the aspect I was coming to on the track - I ended up applying much more throttle much earlier than I normally would. This is a hard habit to do after learning to balance a NA car on the throttle thru a corner. I must confess I managed to loop it once - which is rare for me - once previous in about 6 yrs of track time.
Clearly getting the best performance pre boost would be a big help. I'm sure I'm missing some pre boost power. Just need to find why.
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Alan
Old 06-16-2008, 05:42 PM
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I suspect most lag on a 930 comes from: low compression, restrictive muffler, restrictive CSI metering plate movement, and ignition.

See if the Rice Fueler, a vac sensing WUR is still available, it helps get the metering plate out of the way faster.

Find someone that know what they are doing to re-curve the dizzy so it starts around 7-10 deg and advances to about 33 deg (big low compression motor none boosted motor can take a lot of advance I hear.). Then use a MSD system to bring it back to 24 deg on full boost.

See: http://www.pelicanparts.com/catalog/shopcart/PERF/POR_PERF_msdign_pg4.htm

A k27-7200 comes if by 3k if set up right but limits HP to just over 350. The factory added a larger exaust wheel to it on there C2Turbos that were designed for the track (Andial built 1992 S2's) for less back pressure which would help HP and endurance but increase lag a bit.

More compression w a set of C2 cams helps to. Stock cams if set up right can make more low end power as they actually have a higher effective compression ratio than any other.
Old 06-16-2008, 10:14 PM
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It must be a VERY tight course if, even in 2nd, you have to wait seconds for boost to come in. What RPM are you turning in those cases?

I found after a while that my car was never stock but between SC cam, K27HF & GHL headers, boost actually come in quite progressively (or did I get too used to boost ) which makes coming out of corners very manageable. In most cases, I can go from off boost to at least 0.5 bar boost between turn in & apex.

Now with EFI, it feels even more "transparent" even though I don't use "anti-lag ignition" set up.
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Old 06-17-2008, 08:12 AM
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I had SC cams and an early HF. It did come in more progressively and came in so smooth which was not for me. I liked how the K27-7200 comes in very fast and hard. However, it dose run out of juice up top.

It may not help but I think some turbo drivers can left foot brake in a way to get on or keep on the throttle so boost is up for accel out of the corner.

If I recall, adding the larger exhaust wheel out of a K27-7006 reduces back pressure for a track car.
Old 06-17-2008, 09:45 AM
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Quote:
Originally Posted by hobieboy View Post
It must be a VERY tight course if, even in 2nd, you have to wait seconds for boost to come in. What RPM are you turning in those cases?

.
I could almost count to 5 before boost hits - but I have not checked rpm - but suspect around 2500. I am getting the feeling I am lacking non-boost power and need to find why.
I have just spoken with another guy here who is well known P racer who ran a 930 few years ago. He was using same gear change points as me, and down to 1st on one corner in a tight spot. Otherwise it is 2nd for all corners.
I will need to investigate engine more.
Thanks
Alan
Old 06-17-2008, 12:56 PM
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As I said it should take less than two seconds, providing you are above 2800rpm.
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Old 06-17-2008, 02:05 PM
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A bad/leaky BOV will extend boost threshold higher in the rpm range, increase lag, and decrease power.
I think you should give your engine a thorough once-over and tune up and see how that does.
As for the track and laggy response, as the air heats up the lag becomes worse and the power goes down (you know this). Any weakness in the engine is made worse by those conditions. To compensate for the heat phenomenon I begin riding the brakes on the slow corners while keeping the RPM up.

There are a host of modifications and tuning that can be done to eleminate tubo lag and achieve a boost threshold of 1600rpm. You will have no stock equipment remaining.
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Old 06-17-2008, 03:05 PM
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Hmm - I'm trying to keep it near stock for a number of reasons. If I deviate too much I'll probably end up throwing the kitchen sink at it while in there.
At 2800 I probably am about 2 secs off boost. But off standing start, at least 5 secs, probably more - unlike the link dewolf posted. Below 2800 (2500? need to check) it would seem about 5 secs.
I have had all that stuff off many times over the past months (50?) - but will have another look. I have replaced BOV gaskets.
Thanks
Alan
Old 06-17-2008, 10:59 PM
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The stock 930 has a power band of about 2000rpm, from 3500rpm-5500rpm. That's really not an exaggeration. Is this what you are seeing? I believe that short power band is one reason behind the long gears of the 4 speed. That combination makes for a miserable auto-x or short track experience.
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Old 06-18-2008, 05:02 AM
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Yes - I can see the power band - altho I must say I am very happy with the power that kicks in at 3000. From the discussions so far, I can feel it improve up to 3500 - but it really pulls quite strongly and suddenly from 3000. No complaints above 3000. I have shortened 3&4 for the track to try and make a closer ratio box to try and work in this range as much as possible - given I only have 4 to play with.
But I am fairly sure from this discussion and dewolf's link I am missing useful power below the boost level. I'd be very happy if I could get the beast off the mark like his - no complaints at all. By the same token, I would not be stuck in 2nd under 3000 rpm with foot nailed to floor reciting 'Mary had a little lamb', waiting for something to happen.
I'm pretty sure it is under performing in this range and basically bogging down rather than pulling thru it.
Alan
Old 06-18-2008, 01:11 PM
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Quote:
Originally Posted by Alan L View Post
I am fairly sure from this discussion and dewolf's link I am missing useful power below the boost level.
Alan
If you're running factory timing - (27-29 deg full) - add another 10-deg and you should see significant improvement in low rpm performance. If you're nervous about too much timing under boost (good thing to be nervous about) MSD's multi function ignition control system can readily and reliably pull the extra timing out.
Old 06-18-2008, 04:26 PM
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I am running factory timing - about 26 deg at 4000 rpm from memory and a few deg ATDC at idle.
I suspect there is a problem somewhere and would prefer to find it rather than compensate with advancing timing .
But thanks for thought. If I can get it to run like I suspect it is supposed to do, on factory specs, I think I will be better off than what I currently have.
Alan
Old 06-18-2008, 04:33 PM
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Quote:
Originally Posted by Alan L View Post
I am running factory timing . . . I suspect there is a problem somewhere and would prefer to find it. . . .
Alan
I believe you could learn a lot by adding 10-deg to your timing, warm up the engine and go flog the vehicle a few times just into boost. (Exceptionally good excuse to drive a 930 and you can't hurt the engine here.)
If you do this seat of pants experiment, let us know what you learned.
Chris
Old 06-18-2008, 05:47 PM
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I agree that it sounds like you have a leak or faulty BOV. It shouldn't take 5 secs to spool up no matter how stock your engine is.

How does it run off boost (low revs)? It maybe running rich/lean off boost in the low rev range and you don't notice it when the boost comes in.

Taking off in a stock car from standstill you would probably only count to 2 or maybe 3 and then hit warp speed and travel back in time.
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Old 06-18-2008, 06:30 PM
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Yes - I suspect a leaness - but not enough to cause hesitation/missing. Could be BOV - I had to make up new gaskets. Don't think you can buy them.
If the turbo 'lag' is the actual spooling up between ignition (3000) and lift off (3500) I have no complaints. It feels very progressive and strong. I have not yet really sensed the 3500 peak. From 3000 it just pulls like a JATO.
I have my idle AFR at around 11 trying to correct for this because at race temp under light throttle I'm at about 14 , and previously it was leaning out to 15-16. So, I suspect I'm still on the wrong end of the edge. Once I get that right, I will look at more early advance and see if I can't tweek more from it.
If the BOV doesn't seal well, what happens?
Alan
Old 06-18-2008, 07:33 PM
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Old 06-18-2008, 07:49 PM
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It sounds like once the boost does kick in it is fine but off boost and low revs it is struggling.

I don't know about the fuel head and whether tinkering with it has affected your low down off boost power/torque??

Mine was stock and recently I had a rebuild with 964 cams, a k27"s" and aftermarket headers and it is a lot quicker and smoother than ever but it always seemed to pull strong off boost.

I have also noticed (and this may be my imagination) that if i progressively accelerate as the car builds speed it runs quicker than if I just mash the pedal and wait for the boost. Prolly my imagination.

Remember these cars drive very differently to a Torana in every way (especially cornering).

I hope you find the problem and let us know what you try/find. Good luck...
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Old 06-18-2008, 09:31 PM
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Yes, I agree, mashing the peddle ahead of the torque is not smart. I actually feed the power on just ahead of the torque from a start, but rolling thru the corners once I had no throttle response I found myself with it nailed to the floor simply trying to hurry things along.
I had to do same progressive throttle with Torana anyway - the clutch would just spin if I gave it all at once (even in 2nd). Smoke thru the floor. Bad sign. I don't think it is imagination - I think you do better by feeding the power on.
Part of the problem is I have little to compare to. The car would not even run when I collected it at the port. Had to get a trailer to bring it home. Then discovered a bag of problems that have kept me occupied for 6 mths to get this far.
I think I will pull the intake/fuel stuff off again. Not sure what the BOV effect is if seals no good - suspect more to do with spooling turbo up - lag?
Depending on what we define as lag - if it is the zone between picking up power to max power, I suspect I have very little. I am very impressed with it in this zone - it is extremely driveable and once in this zone from 3000 up, you can balance it on the throttle in the corners pretty well. Some nice power slides (not intentional).
Alan
Old 06-18-2008, 09:55 PM
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Alan,
Before you tear into your engine again, can you find someone who is familiar with STOCK 930 that can drive your car for you? It is within reason that there may be nothing wrong with your car. With mods so prevelant and the technology so old/unique a stock 930 can leave the impression that there is something wrong with it.
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Old 06-19-2008, 05:12 AM
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Quote:
Originally Posted by 356-930 View Post
I believe you could learn a lot by adding 10-deg to your timing, warm up the engine and go flog the vehicle a few times just into boost. (Exceptionally good excuse to drive a 930 and you can't hurt the engine here.)
If you do this seat of pants experiment, let us know what you learned.
Chris

Chris, Are you saying to set his timing at 36 deg at 4k instead of 26?? Can he safely do that with a stock engine without getting detonation?
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Old 06-19-2008, 06:04 AM
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