turbo problem

[CBR900RRGS]

Before I get started, this motor is being used in a racecar. I have a 1300cc motor with 1500cc stroker kit installed. Here is a list of mods. 48mm throttle bodies, 40 pound injectors, carillo rods, custom pistons, custom cams, billet crank, ported & polished head, titanium valves and springs and the whole assembly is balanced. We justa added a Turbonetics turbo and an intercooler to the motor because it did not make enough power. Once the turbo was install, we took the car to the track and we had problems with the turbo. Between 6000 & 7000 rpm, the engine will cut out for a split second and then continue throught the rpm range. we have tried bumping up the fuel pressure and made some modifications to the fuel map with no luck. The inside of the exhaust pipe is still white so that tells me that it is still running too lean. Does anyone have any suggestions?

[STUNNAH]

This maybe a stupid response...But what are you using for the driveAre you also using the tranny...If you are it could be a gear...Just a thought...

[STUNNAH]

Also, I'm running a Velocity Stage 1 street...At 6pds of boost my fuel pressure is set at 70pds...I guess the FMU adjusts the fuel pressure for the 8pd setting...

[CBR900RRGS]

I am using the stock transmission and gearing. The gear box has been gone through and beefed up a little. It would not be a gear issue because it happens at a certain rpm range and not in a specific gear.

[STUNNAH]

Just throwing that out there because that's exactly what my bike did when 2nd gear went out same spot every time...The power would skip just for a milli second and whamp back on...Replaced the gears and she pulls like a champ...

[CBR900RRGS]

This happens in every gear. As soon as the the problem clears up, it will climb all the way to redline. we just can't figure out what the prolem is in that rpm range.

[MET]

What size is the turbo??

Is the turbo spiking and then dropping back down?

Sounds like the boost is pushing so much into the large throttle bodies that it may be working hard on the valve springs. You need about as heavy as you can get. What are you using??

Sounds just like my Busa was doing before I did the engine over for rebuild.

You have large t-boddies and a ported head, does the same problem exsist at any amount of boost?

[CBR900RRGS]

I do not recall what size the turbo is. we were told that this turbo on the the motor that I have would have no problem making 400hp. The turbo pressure and the fuel pressure are not spiking. The valve springs are the heaviest that we could find. We are only running 11 pounds of boost at this time. We are planning on taking it up to 25-30 pounds. we are below stock compression. The problem is only occuring at 6000, then 6500, then7000. Then it lights the tires up. The exhaust pipe is white so I think we are having a fuel delivery problem. I am running the stock computer with a power commander for adjusting the fuel map. I have found out that tuning for a turbo is not the easiest thing to do. I have been putting very little time on the motor because i have about $45k-$50k tied up in this motor and I do not want to blow the thing up.



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[MET]

I hear you on the blos up portion. Yes you do not want to do that.

Injectors sound like they are not spraying all the way. I would agree that you are not getting enough gas. I have found with the poser commander that you need to bring the mid and the high both up. If you do not bring the mid up it dips before the high can kick in. Once the high range kicks in you have plenty of gas. Just a hunch? Try bringing both the mid and high up all the way. Then if that works back down a little keeping the mid 1 or 2 clicks down from the high.

[CBR900RRGS]

We just put the 40 pound injectors into it to see if it helps. They are brand new. We were running 32 pound injectors. I am going out to Sears Point on Friday to test it out with this change. I hope that this solves the problem. I know it is running lean right now so I do not want to melt a piston in the process.

[CBR900RRGS]

The 40 pound injectors did not help. They were way to big. We had gas dripping out of the exhaust pipe. So we pulled the motor out of the car and it is going on a dyno tomorrow. We are going to put 35 pound injectors in it because the Power Commander has limits on how much we can adjust everything. We have ran out of adjusments. Plus the shop doing the dyno work knows what they are doing.

[MET]

Originally Posted by [b

Quote[/b] (CBR900RRGS @ Feb. 02 2005,02:02)]The 40 pound injectors did not help. They were way to big. We had gas dripping out of the exhaust pipe. So we pulled the motor out of the car and it is going on a dyno tomorrow. We are going to put 35 pound injectors in it because the Power Commander has limits on how much we can adjust everything. We have ran out of adjusments. Plus the shop doing the dyno work knows what they are doing.

No limitis on the adjustments before the power comander on the Dyno. *The comander will (as you know) give you fine tunning, once yu do the Dyno and do the timing and the throtle and the mixture with a sniffer.. *B

What type f rising fuel regulator you using??



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[Uncle Bob]

with a good, variable FPR and big injectors, if that doesn't give you enough range to work within the parameters of teh commander, there is something else wrong, plain and simple. I wish I could offer some advice other than to recheck what you've alread checked. Its not the injectors and its not the computer, from what you're discribing......somethings going on though, thats for sure.

[CBR900RRGS]

The major stunmbling problem has gone away. The only problem that we are having now is with the injetors and the Power Commander. We are running out of adjustment on the Power Commander for the fuel map. We have tried to compensate by changing the fuel pressure, but that did not give us as much room as we needed. I will keep you guys posted on what happens and what kind of numbers this thing is going to put out.

[MET]

What are you using for a fuel pump??

[CBR900RRGS]

It is a Bosch fuel pump. It is capable of putting out 60+ pounds of fuel pressure. I am not totally sure what brand the fuel pressure reguator is.