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Thread: Re: Bucking under boost?
01-25-2007 08:06 PM #1
Re: Bucking under boost?
I apologize for not updating my post from 5 months ago, but it has taken that long to shake things out. I saw no other way to resolve my problems than to send the car to AA and let them sort it out. The only good covered transporter I found that would do a Minneapolis to Miami delivery cost $1,500.00 EACH way…but I was stuck. The car with at least 15K in modifications (complete suspension, heavy duty clutch, lightweight flywheel, custom differential mount upgrade, bigger custom radiator & oil cooler, etc., etc., etc.) and another 16K into the turbo system and it drove so poorly that I’d have a hard time selling it for 15K! So off it went in expectation that AA would get it right.
Karl Hugh has been very good about staying in touch with me, and they have been working away for the last 2 months. That sounds incredibly long, but in their defense they got the car days before the Thanksgiving holiday, then their Dynamometer broke, then there are the Christmas and New Years holidays. And, I said I wanted them to drive it and really shake it down before putting it back on the trailer. At this point much time and money had gone into the car and I wanted to be sure it is right, a few extra weeks are fine with me
I apologize for an extremely long post, but I am not technically able to give a concise and accurate evaluation of the process. And I'm guessing those whose eyes don't glaze over will enjoy digesting the process AA went through. (I omitted my input for brevity believing Karl’s reports are of more interest and enlightenment.)
Karl’s reports have been:
We did get the car yesterday, it is a nice car. So far we took it for a quick spin and even with the boost control off, the boost is still going past 15 psi!!! Did you know about this? Please email me a list of the problems you have so we can look it over methodically.
Barry took the car out and did verify that the boost is overboosting so we took the car and put it on a lift to check the wastegate, it was rusted shut, not sure why, but the valve is all pitted and the housing is all rusty. We removed it and it is not really worth repairing, the shaft is too bad. We have ordered a new one already and should have it here by tomorrow. We will install it and then go from there. I will let you know more after we install the new one and do some more testing.
We have the new wastegate installed already and that is fine now, we can control boost, we are having a small misfire and we suspect spark plug or spark plug gaps too big? We will have the car in the shop again tomorrow and we will have more information for you by Tomorrow or Wednesday. We are hoping to have it on the dyno for the testing, that way we can check air to fuel, boost, HP T etc.
During a tuning session we had a fuel delivery problem and found that as we passed 11 psi we started to have fuel pressure fall off. We removed the passenger seat and removed the fuel pump, we installed a higher volume one and that is fine now. We then strapped the car down on the dyno once more and the power is good, but again we have a problem when we pass the 12 psi boost mark, the HP and T takes a nose dive, we discovered that the catalytic converters are partially clogged and so as we move more air and exhaust flow we now have a choking problem in the exhaust. So far the rear wheel HP is around 310 at 11 psi and we hit 350 at 14 psi but nose dives after 5000 RPM. The car is back off the dyno. I need to know what you want me to do from here.
(On my approval they replaced them with high flow cats.)
The car is on the dyno now, we seem to be having a small knocking problem or something with the knock sensors, the power is not bad but the curves are not smooth and slightly up and down. Will know more by tomorrow. Low boost ~10 psi is making ~315 rwhp.
I have some questions:
1) do you have any other cams in the car that are not stock?
2) was any other work done on the car engine
3) Is the Schrick intake manifold extrude honed?
4) Any Specific Dinan mods on the motor or fuel system?
We have been experiencing a nasty dip in power between 5K and 6K, and then the power comes back up. We checked a ton of stuff and we could not find anything wrong, so we did the basic tests, compression, cam timing etc.
Compression is very even at 120 psi (a bit low to me, I expected to see maybe 140-145), so I am thinking that you may have some high lift high duration cams in there?
I did some custom tuning on the ignition maps for this lower compression and I was able to get that nasty dip out, this is ok, but it bugs me that maybe there are some high duration cams in the motor? Please answer the questions above so I can have a better understanding of what I need to do.
(There were no engine or cam modifications other than an AA supplied head gasket to lower the compression, AA supplied fuel injectors, and a Schrick intake manifold which as the installer said "don't think so but the ports were very smooth, while still showing evidence of sand-casting".)
I have attached the latest dyno runs from this morning. Look at the notes I made on it, this is the dip that we are trying to remove, but to no avail. I suspect that the dip is caused by the Schrick intake manifold, I have never tuned one with a Schrick intake manifold before. My recommendations is to install an OBDIM3 manifold, we have seen very good results with that. Other than an OBDI , we can only go back to a OBDII one, we will lose some top end power but will have very strong midrange and bottom end. I really cannot spend any more time on the car with the hardware the way it is, software cannot fix this dip, we have been trying all sorts of things in the last couple of weeks and no real luck. Power is good at peak ~ 359-360 rear wheel HP, which translates to around 440-450 flywheel HP. Call me if you want to discuss the chart
the car is done, we found a used M50 intake manifold from 95 M3, made up the necessary brackets and connectors and installed it in the car, retuned the software and now we have it running very nicely. The car is a beast on the road!! We are in the process of making you a nice heat shield around the HFM. I will take it on the road again tomorrow to shake it down some more before we give you an OK to arrange shipping it back. I will also go over your bill and get you a copy with all the breakdown. Here is a dyno chart of the car on low boost 11 psi and high boost 15
psi. This is rear wheel HP so to go to flywheel HP multiply by 1.29-1.31
Thanks for everyone's suggestions and I'll post a final report once everything is worked out and I actually drive the car!
All the best,
ps I will try to post the dyno charts next week, I'm currently traveling.
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