Stuttering Topend Please Help

[NeOzz1]

Car runs fine until it get to about 5900-6000 rpms then it starts to stutter.

mods
evo3 16g
full 3 inch
sbr manifold
10psi!
walbro 255
fpr

other minor stuff

1st gear till redline no problem
2nd gear till about 600-6500 stuttering starts
3rd 6000-6300 stuttering starts
4th 5900-6000 stuttering starts
5th have not revved it that high

any ideas would be greatly appreciated

I just bought the car so I can only answer so many questions but go ahead and ask if it will help me fix it

 

[NeOzz1]

darn i was hoping that was the problem causing the stuttering, ok i will test

 

[NeOzz1]

I feel very dumb now, I figured out the problem, well it makes sense that it would be anyway, my boost is set to 10psi but it is creeping all the way to 21 it creeps to 21 right before it starts suttering, i did not notice cause i was busy watching th a/f and trying to figure out why it was doing it in the first place.

 

[oldman]

I feel very dumb now, I figured out the problem, well it makes sense that it would be anyway, my boost is set to 10psi but it is creeping all the way to 21 it creeps to 21 right before it starts suttering, i did not notice cause i was busy watching th a/f and trying to figure out why it was doing it in the first place.

No offense but there isn't really a good excuse for this.

1. Why are you looking at the a/f gauge, it doesn't tell you anything.
2. Even if you were not looking at the boost gauge, you should have notice the difference between 10 and 20 psi.

With that said, this is what you need to do to address creep. This however doesn't mean you're off the hook on boost leak and fpr overrun, they still need to be addressed. Good luck.

 

[NeOzz1]

thansk for all the help I will elt you know what happens

 

[NeOzz1]

Ok pulled it apart to do the port work and decided I mite as well fix my manifold studs and move the sidemount into the wheel well more. When I pulled it apart I found that it was already ported, I ported it more though and made it so the flapper wold open more then 50-60 degrees. Here are the pics.

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Before I ported the wastegate

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Before I ported it more

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After

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After

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After

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After

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[oldman]

Not bad and I think you get the idea on where to port, just some suggestions since you have tools to port.

1. More work can be done to the inlet, the step should be completely invisible, match the manifold collector and the turbine inlet to a 7cm gasket. The finished pictures also are dark and hard to see, next time shine some light into the inlet when you take a pic.

2. If you still have the stock o2 housing, enlarge the entire flapper/wastegate path area and match your O2 housing side like this.

3. Finally, Make sure the O2 housing is matched like this.

When it comes to porting, don't try to do just enough, instead everything you can without obviously cracking the housings. Don't take any chances of having to remove them again for re-port.

 

[NeOzz1]

Not bad and I think you get the idea on where to port, just some suggestions since you have tools to port.

1. More work can be done to the inlet, the step should be completely invisible, match the manifold collector and the turbine inlet to a 7cm gasket. The finished pictures also are dark and hard to see, next time shine some light into the inlet when you take a pic.

2. If you still have the stock o2 housing, enlarge the entire flapper/wastegate path area and match your O2 housing side like this.

3. Finally, Make sure the O2 housing is matched like this.

When it comes to porting, don't try to do just enough, instead everything you can without obviously cracking the housings. Don't take any chances of having to remove them again for re-port.

1. Yeah I was probably going to do more because its not quite smooth enough, I cant bring the wastegate side out to much more though its out alot.

2. I got it, rnr 3 inch o2 elimnator so i cant do much, i did put the o2 gasket thing on while i ported the turbo then matched that part so it does open all the way in there too.

3. #2

 

[NeOzz1]

btw my wire wheel dont fit in there so i cant use it

 

[NeOzz1]

did not fix the problem at all, still climbs... if the side of the bcs was plugged itstead of goin to the wstegate but the other side that goes to the intake was still on the intake would it cause creep?

I am so lost know... i know it opened 90 degrees and i know it was ported enough,

Is it possible that something else is causing boost to rise?

External wastegate i guess

 

[oldman]

did not fix the problem at all, still climbs... if the side of the bcs was plugged itstead of goin to the wstegate but the other side that goes to the intake was still on the intake would it cause creep?

No.

I am so lost know... i know it opened 90 degrees and i know it was ported
Is it possible that something else is causing boost to rise?

Just one more thing, just because the flapper is capable of opening more doesn't mean the actuator arm extends long enough. Apply compressed air to the actuator and make sure it's extending all the way and that when it does, it's not hitting your DP.

External wastegate i guess

Maybe, make it a manifold mount though, an O2 mount will most likely get you the same results.

Sorry it didn't work out, you suck.

 

[oldman]

By the way what is your boost setting and where is it creeping to?

 

[NeOzz1]

Set at 10 and creeps till ... well it hits about 21 and starts to stutter, usually i dont let it do that now that i know thats when its doing it


whats is a 38mm external good for? i have plans in the future for a much faster car and if i am going to do it mite as well do it right the first time

 

[oldman]

If your goal is 350-400, you really wouldn't need to worry about creep because you will be boosting more than 20 psi anyway. If you're creeping to 21psi with the mbc turned all the way down (minimum boost), the most you will creep to as you turn up the boost should be 21 psi or less. I suspect that your creep might end if the boost is set at 19psi, higher boost setting = longer spool = less time to creep) leaving things the way it is.

I'm still baffled as to why this didn't work for you. Did you check to make sure the actuator is functioning probably and able to fully extend the arm and that the flapper isn't hitting your DP?

 

[NeOzz1]

I know it has the room to open all of the way but i dont know if the actuator is pushing it that far, how can i test to see if it is, prefurably not taking it apart again but whatever it takes




what type of hp or 1/4 is a 38mm tial good for?

 

[oldman]

I know it has the room to open all of the way but i dont know if the actuator is pushing it that far, how can i test to see if it is, prefurably not taking it apart again but whatever it takes

Apply compressed air directly to the actuator while you observe, you should now have a decent idea where it should open to since you have just worked on the flapper.

what type of hp or 1/4 is a 38mm tial good for?

I do not know but I'm sure a simple search will net you an answer.

 

[NeOzz1]

have not had time to test the actuator but i found a used tial 35mm and he said he would sell it to me and weld it on for only 130

btw what should by fuel pressure be set at?, with the line on or off? if i take it off do i plug both spots it was hooked to?

thanks justin

 

[oldman]

btw what should by fuel pressure be set at?, with the line on or off? if i take it off do i plug both spots it was hooked to?

With vacuum line off, 37psi. Just put your finger over the open line while you make adjustments.

 

[NeOzz1]

so pull the line off the fpr put my thumb over the open tube, then adust the fpr in/out? until it says 37... then put the line back on? what should it say when i put the line back on? or does it not matter?

 

[oldman]

so pull the line off the fpr put my thumb over the open tube, then adust the fpr in/out? until it says 37... then put the line back on? what should it say when i put the line back on? or does it not matter?

That would be correct. When you re-attach the vacuum line, the gauge should read 37psi - your vacuum reading in psi. A 1g, with stock cams, should read about -18 to -20hg which equal to -9 to -10 psi. Therefore your fuel pressure reading should be 37psi-9psi = 28psi. Now you know your B&M 43psi at idle was way off.

 

[NeOzz1]

OK its the actuator arm for sure, it does not even move as much as the wastgate would open before i ported it, whats the solution to this?

i did not use air i just clamped to it and pulled, i know it was pulled all the way because it stopped, its not like i ran out of pulling power it actually stopped

it only moves about 1/4 of the full length to open the wastegate

 

[NeOzz1]

bump