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BOOST PROBLEM CURED, thanks for everyone's help

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
Hi again. Thanks to everyone who answered my post about my drastic power loss problem. The electrical connector to the Microfueler had come loose (special thanks to 90Callaway). I don't know if many of you have seen the connector I'm talking about but it's a kind of round DIN connector only held in place by a plastic screw on clip which has broken on my car. I have plugged the connectro back and all my performance is back but I suspect that all it will take to dislodge the connector agian will be a drive over a bumpy road. As 90Callaway suggested tomorrow I'll try and secure the connector better with a plastic tie wrap or hose clamp.

Doesn't take much to take all those horses away does it???!!!

Thanks again folks, you're the greatest!
 

TAC

Well-known member
Joined
Feb 18, 2002
Messages
252
Location
Bothell, WA
Corvette
1987 Yellow Callaway TT Convertible & 2003 MY Z06
I read the stuff below at the Callaway website when I saw your post. I got to this part about the Microfueler--"With the exception of relying on the fuel pump for pressure and the tach connection on the distributor for engine rpm it is 100% independent of the car's engine control system" and quit reading since it sounded like the Microfueler doesn't control boost condition. I am still a little curious as to how the Microfueler failure caused boost to go down. I would have guessed--as they say--you would simply go way lean and damage the engine. Oh well...glad you got it fixed.

"The next thing to look at is the "Microfueler" system. This system consists of the additional injectors mounted on the "rams horn" (the casting in front of the throttle body), a black box, a wiring harness, and a fuel hose connection from the fuel rail at the intake manifold. This system is there to provide additional fuel to the engine under boost conditions only. The injectors are driven by the black box mounted on top of the kick panel over the drivers knees. This box senses engine RPM and manifold pressure, and drives the injectors accordingly. With the exception of relying on the fuel pump for pressure and the tach connection on the distributor for engine rpm it is 100% independent of the car's engine control system. Failure of this system will cause a lean condition in boost that will at a minimum make the car feel down on power, and at worst will cause engine misses and/or detonation. Another possible failure with this system can cause it's two injectors to be held open constantly when the ignition key is in the run position. This will flood the engine and cause a no start condition. If disconnecting the electrical connectors at the injectors enables the car to be started than there is a problem with this system."
 

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
Boost problem cured

Hi TAC, maybe I should have said IT FELT like the boost went away. It was probably the lack of fuel supply that caused the car to feel severely down on power.

I take your point that the turbos are not controlled by the microfueler. My problem was caused by the Microfueler electrical connection becoming diconnected.

Take it from me, when that happens you no longer have a performance car!!!


All the best, Malc.
 

TAC

Well-known member
Joined
Feb 18, 2002
Messages
252
Location
Bothell, WA
Corvette
1987 Yellow Callaway TT Convertible & 2003 MY Z06
Ok...that makes more sense. For sure I'll file this tidbit for future reference. Glad it's working again. I know what it's like to lose the turbo power. NOT a happy feeling!
 
9

90Callaway

Guest
Glad you got it fixed!!!

Hi Malc - I was away for the weekend and just saw that you got your problem resolved. That is EXACTLY what happened to mine.

TAC - You are correct that the microfueler has no direct control on boost level. However, the car will run so poorly when the secondary injectors are not firing under boost that it will drop off and become very erratic. The engine is missing so badly that you won't have sufficient exhaust pressure to achieve and maintain peak boost. This is one of the MOST dangerous conditions that can happen with a Callaway. Do NOT drive your car under boost if you are experiencing these symptoms.

Another serious problem would be overboosting. The only direct control on peak boost is through the screws on the wastegates. However, changes to the exhaust system will change boost level by reducing back pressure. My car makes 52-54" of boost with the cat on and 58" with it off. I could change this with the screws of course. If you have access to really good fuel (94 octane or better) you can safely run 58" of boost and make LOTS more power than you do at 52".

Leaks in the intake plumbing can cause low boost and make you loose power but that's not really dangerous in terms of grenading a very expensive engine.

One final tip - After I used a small size plastic wire tie on the cheap plastic teeth that hold the screw on part of the connector to the body and locked it down tight on the microfueler I wrapped the whole connection and up onto the cable with black vinyl electrical tape to provide addtional strain relief.
 

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
Microfueler problem

Cheers 90 Callaway. The clip you refer to had a split in it so I wrapped it with a tie wrap. I also put a bit of foam around the microfueler so it wouldn't rattle about so much. I can't believe it isn't even secured!!!

P.S. Is that boost tip for real? My car has no cats and Stan A contacted me to say he would advise my local turbo shop how to increase the boost though he didi say it's a bit hit and miss.

Trouble is I'm not sure what his tip involves and if it means removing the turbos I don't want to do that unless I really have to, like if I'm having the turbos rebuilt.

Let me know if possible how to change the wastegate setting and just as important, how I can tell how far I can go without blowing it up!

I'll be taking my car to the drag strip within a couple of weeks. If I get a good time I'll post it (if not I'll keep quiet!).

All the best, Malc.
 
9

90Callaway

Guest
Would I lie to a Callaway brother?

:) Of course not! Yes the boost tip is for real. Notice that with the car off the boost gauge reads approximately 30". That is inches of mercury as in barometric pressure. One atmosphere is 14.7" of pressure give or take a little bit. So, two atmospheres or 60" on the boost gauge would be around 14.7 (call it 15) pounds of boost. Therefore each additional inch of mercury will be giving you close to 1/2 pound of additional boost. If you are at 50" now going to 58" would give you about 4 pounds more boost. You'd be going from around 10 pounds up to 14. You may want to stay around 56" if you're nervous about getting quality gas all the time. I think you said your gas is fairly high octane. I don't know if it's rated the same as ours. The best I can get is 93 octane unleaded so I run about 1/3 114 octane race gas. Callaway was very conservative in setting these cars up since they had to warranty these things! The additional boost should get you somewhere in the 75-100hp range at the wheels and a healthy dose of torque. A well set up Twin Turbo ('88 or later) with untouched engine internals will make 500hp and 700lb/ft of torque at the wheels. That requires the Callaway Wonderbar intake, quality high flow exhaust and around 14" of boost with NO leaks anywhere.

It is a fairly simple procedure of loosening a lock nut on the wastegate of the turbo and turning an adjusting screw. You don't need to take anything apart. They do need to be turned evenly. Somewhere I've archived a detailed write-up of the procedure. If Stan doesn't get time to send it off to you let me know and I'll hunt it down.

Good luck at the dragstrip! I didn't even know they had them over there! What kind of cars will you be running against? Let us know how you do!

Cheers!
 

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
More boost!!!

Cheers 90Callaway. I'd sure be grateful if you could post the procedure for adjusting the wategates and I reckon a lot of other Twin Turbo owners would!

The main thing I'm curious about is how I'd know that I've adjusted each wastegate an equal amount? Is it just a case of turning each screw the same amount of turns?

Something tells me there's more to it than that.

By the way my car has a free flowing exhaust with NO cats.

Regards, Malc
 
9

90Callaway

Guest
I thought you might say that...

I will start combing my archives for this. I don't think I'm going to post it here though. I don't want to be associated with anyone blowing up their car. Do you guys have the saying over there, "A little knowledge in the hands of the wrong person can be dangerous"?

I will get it to you. If anyone else wants it, feel free to email me.

Cheers :beer
 

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