RX1 CPR turbo stutter problems

[69camaro]

I have an 05 rx1 with a CPR turbo, drag sled only. It has an MC4 ignition with MSD boost controller. The problem I am having is that the stutter only works well when the sled is cold. By cold I mean first pass of the day with the sled having been warmed up to about 180 and cooled back off to about 120. The stutter will work perfect every time the first pass. Will build 10 lbs of boost in about 2 seconds at 4800 rpm. Make a pass, cool sled off, line it up again, stutter will not pop hard at all. Maybe 1 or 2 pops and thats it, its just limiting rpm. It almost acts like its not pulling the timing out, but after checking the laptop the datalog is saying timing was pulled. Will only build 1 or 2 lbs of boost. Anybody ever encounter this problem before? I have heard its possible that it may be jetted to rich? It does seem to work better in winter, although I did have the same problem a few times last winter. Im running 152.5 main jets and 15 pilots. I pulled the carbs off and they were spotless, still cleaned the carbs thoroughly and it made no difference. Im running out of ideas...

 

[mbarryracing]

Yup it's too rich after everything is heat soaked after sitting after the first pass, it's drowning the fire out. Combustion chamber temps, oil temp, intake air temps, etc all playin a roll.
You are going to have to play with the needle clips so it 2-steps when up to temp (hot) then you can always work around getting everything up to that same temp for your first pass.
Consistency with carb's and 2-step's are tricky because of temp, even on my fuel injected Apex if it's been sitting after shut-off and it's heat soaked, the 2-step doesn't work very well either because of the intake air temp from the components soaked up the heat.

 

[69camaro]

Alright I will drop my needles a notch and try it, hopefully this saturday. Its hard to repeat in my garage, just plain dont get enough heat soak running it on a stand to compare to making a pass. Clips are in the center notch currently, so I can drop the needle 2 notches yet. How sensitive is it? Hopefully I can get away with not having to get a leaner set of needles for summer use.

 

[69camaro]

Dropping the needles one notch did not help at all. Only difference it made was being too lean on the needle. I may try richening it up just for kicks and see what happens.

 

[kingtut]

I have the apex version of your sled, but I never got the launch control to ever go off. No idea what triggers it to go off. Turned it off by making the rpm to 0 and i go just fine. Those things are so touchy i swear.

 

[69camaro]

An MSD launch master will not make the sled pop and bang and build boost. It only limits rpm so you can hold it full throttle at a preset rpm and then let go of a button, or whatever you have triggering it, to take off. It will build maybe 1 or 2 pounds of boost. Im running a full MSD MC4 ignition and separate MSD boost controller with an external wastegate. When everything works correctly, it will build 9-10 psi in around 1 second. The problem is getting it to work consistently all the time. Simons stuff does make power, but I am not a fan at all of the setup. I wish I could afford to build a turbo sled from scratch, because I would do it very differently. The other issue is this is a drag sled, with clutching and suspension setups based on leaving with a certain amount of boost. Leave on 10 and build to 26 in 1.3 seconds. Problem is when the stutter doesnt work and you leave on 1 or 2 psi, the sled is a dog and you can wave goodbye to whoever was in the lane next to you.

If you want help with your launch master Im sure somebody would be willing to help. Im not too familiar with them, but I can look into it if you would like. Im sure you need to turn it on and off somehow, and set your rpm you want to limit it at, and a trigger of some sort to activate it. Do you have the instructions for it? I thought I read somewhere they make one specifically for an apex?

 

[kingtut]

I found the manual for it. I just gotta trace some wires. it might be hooked up through the brake light or something.