woohoo, no boost

backtobirds

Registered User
After the rebuild, diagnosing what turned out to be a bad crank sensor mount, and exploding the trans on the test drive around the block I have the car back together and driveable. Also got a Moates Quarterhorse for tuning. Props to those guys, that is probably the best EEC-IV tuning product I have ever used. Plenty of fun to drive and it sounds like a big block, but I can't get any boost out of it.

A little background, new block, rotating assembly, SSM heads, ported intake, MPX case and plenum, 10% crank pulley, 10% jackshaft, 10% blower pulley, cam, and long tube headers. So I would expect some boost but it barely creeps to maybe half a pound. So, for what it might be:

Head gaskets are of course new, ARP head studs, 99 block so the threads are countersunk an extra inch for better gasket retention. No evidence at all of gasket failure, and it showed 160 to 170 psi on a compression tester.

Intake-torqued, retorqued, dry and thread-locked.

I am using teflon gaskets on the blower outlet, return plenum-to-intake manifold, and return tube-to-return plenum. Turbonetics silicone couplings for the FMIC piping.

Put the blower together with anarobic gasket maker and torqued everything. I had a problem with the bypass plate sticking, so I sent it back to Charles and he opened it up a little to free it.

Still no boost. The car pulls 18-20 inHg at idle and I sprayed all the connections and gasket areas with brake cleaner, as well as the intercooler. I even did all this with the bypass manually closed as well, but came up with nothing. Just to double check my butt dyno and boost gauge I took a datalog. The MAF follows the throttle position sensor just fine until the TP is opened up, but then it only shows the engines natural air capacity and no more. Score one for the butt dyno I guess. Anybody have an idea what might be going on?

Here is the datalog if anybody wants to see.
http://www.mediafire.com/?xciiygy1wyl
 
I took a look at that thread. I hope that isn't the problem, as I can stick my finger between the rotors to hold them and twist on the pulley, but it isn't slipping doing that.
 
Do you have the boost gauge hooked up to the return plenum, because if hooked to the inlet plenum, it will only read vacuum. Are you certian that the boost gauge is working ? It is possibly that it will only read vacuum if gauge gets clogged up with gunk...had it happen to mine from using nitrous. It's easy to test the boost gauge using an air compressor with pressure regulator turned down to about 10 psi...just supply the compressed air to the gauge hose.

I'm asking about the boost gauge, because if it runs like a big block, then it has to be making boost. Without boost a low compression 3.8 will barely get out of it's own way.

David
 
Do you have the boost gauge hooked up to the return plenum, because if hooked to the inlet plenum, it will only read vacuum. Are you certian that the boost gauge is working ? It is possibly that it will only read vacuum if gauge gets clogged up with gunk...had it happen to mine from using nitrous. It's easy to test the boost gauge using an air compressor with pressure regulator turned down to about 10 psi...just supply the compressed air to the gauge hose.

I'm asking about the boost gauge, because if it runs like a big block, then it has to be making boost. Without boost a low compression 3.8 will barely get out of it's own way.

David

No, it just sounds like a big block. Actually louder than a 5.0 Mustang I had. The gauge is hooked up to the stock location. I checked the gauge as well as the airflow (the datalog). When the bypass closes nothing happens.
The blower hub doesn't seem to be slipping on the shaft, but I don't know how much force is put on it under boost. I would imagine however that if I can hold the rotors and turn the pulley and it doesn't slip that would be good enough. I also wonder if the rotors and MPX housing aren't sealing, but Charles said that's not possible...... Just more down time I guess.
 
Make sure the spout jumper is plugged in. It almost sounds like the car isn't making any timing and is stuck at 10 degrees, which would make it choke on itself going into boost.

Datalog spark, rpm and vmaf and see what your getting commanded wise for spark.

Fraser
 
Make sure the spout jumper is plugged in. It almost sounds like the car isn't making any timing and is stuck at 10 degrees, which would make it choke on itself going into boost.

Datalog spark, rpm and vmaf and see what your getting commanded wise for spark.

Fraser

I was having a problem with the spark where at initial throttle it would pull around 40 degrees. i traced it down to torque limiting. i don't know how it works, but i set some spark tables to zero to make it driveable. The spark would recover instantly, but still no boost.
 
What year is your car and what is the catch code for the EEC?

And just what tables did you zero out?

Fraser
 
What year is your car and what is the catch code for the EEC?

And just what tables did you zero out?

Fraser

It is a 95. Catch code is P5X0, strategy is CBAZ0. BE is the only program that supports CBAZ0 that I know of, but you can still view the strategy and bin without registering. I zeroed the "Spark Torque Limiting for Torque Ratio" table, it was the one going WAY negative. I don't intend to leave it that way, but it is a temporary fix until I figure out how that torque limiting process works.
 
What did you do to your tune to take into account a blown setup instead of a N/A setup?

Not saying you haven't done anything but just curious.

Fraser
 
So far I have just made the changes for the hardware. Injector settings, injector timing from the cam, MAF transfer, etc. As for the rest, I am going to use my wideband and knock sensor to get everything close before putting it on a dyno. But I can't do any of that until I get the boost problem fixed. Are you thinking they are related?
 
The stock N/A tune is set up for a motor that will probably never see more than 70% load at WOT, so all the fuel enrichment and spark tables are set up accordingly.

Add a blower, and now your seeing about 120% to 130% load (super coupe setup) almost the second you put your foot down, meanwhile the spark isn't there to support it and neither is the fueling, which by the way may be to lean for a boosted setup as we typically target 11.7.

Was the car originally a n/a 3.8 with a distributor?

Fraser
 
The stock N/A tune is set up for a motor that will probably never see more than 70% load at WOT, so all the fuel enrichment and spark tables are set up accordingly.

Add a blower, and now your seeing about 120% to 130% load (super coupe setup) almost the second you put your foot down, meanwhile the spark isn't there to support it and neither is the fueling, which by the way may be to lean for a boosted setup as we typically target 11.7.

Was the car originally a n/a 3.8 with a distributor?

Fraser

It sure was n/a with a distributor. i can datalog commanded a/f and load. can also try it without the belt. i might have to play with load scaling. but i should note that it doesnt fall on its face, just doesnt make boost. i would think that at 4000 rpm with the throttle open and bypass closed it should make boost regardless of what the tune is doing. but hopefully i can datalog tomorrow. forgot i have a project due at the end of the week.
 
If people can hear you whining from far away, then how is it not making boost? :confused:

that would be my dilemma
actually, it may be making boost but not getting anywhere. I cant find any leaks though. and i haven't considered that the intercooler may be clogged. i should check on that.
 
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I had the same problem, errrrrr from the blower, just no boost on the gauge. So i pulled it and resealed everything. Cranked it up, lower idle and less vacuum. I didnt drive though, burning fuses, crushed wires, etc.....

Justin
 
The tune is WAY off and doesn't support a boosted setup. If the timing isn't right as well as fuel demand, it will not make boost much over "0" because it'll fall flat on its face before boost has a chance to build up.

It would help to tell everyone exactly what car that motor is running in and what it was originally.

Have fun working out the problem ;).

laters
Fraser
 
The tune is WAY off and doesn't support a boosted setup. If the timing isn't right as well as fuel demand, it will not make boost much over "0" because it'll fall flat on its face before boost has a chance to build up.

It would help to tell everyone exactly what car that motor is running in and what it was originally.

Have fun working out the problem ;).

laters
Fraser

The car is a 95 LX 3.8 with a SC based engine. when i get home i will put up a link to the datalog, as well as compare my tune to a SC tune. you sound like you have been inside the eec before, any pointers?
 
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