ok so i have a 351w with victor jr heads 1.7 rockers F 303 cam pp spyder intake and a turbonetics 76mm turbo .96 A/R with F1-68 turbine wheel oil and water cooled.

so the question is im running about 8.5 psi with just the JGS wastegate and then on the AEM TRU boost controller i turn it up to about 14.5 but the car does not seem quicker at all.im guessing going from 8.5 to 14.5 should be 60hp easy but the car is not quicker at all and if it is its nothing i can feel so what would be causing this?i had someone data log it and the tuner does not have shit for timing init.it goes from 14total and 11 degrees of timing.anything over 8psi timing goes to 11 could the timing be the issue?

i still need to get it retuned but before i do i want to make sure i dont have any other issues that could be causing this.

 

Should feel noticeably fast from 8.5 to 14.5 even with dropping 3 degrees timing. What valve springs do you have, maybe it is valve float, thats easy to achieve in turbo engines, I had the exact same experience as you and it was floating the valves with more boost, seems to run smooth, but just no more power. Or maybe it is going a little lean, that will slow it down too, among other bad things.

 

its the stock valve springs on the victor jr heads

 

What fuel, and comp ratio? How many miles on the springs? Ever checked IAT's, or back pressure?

 

I would try and get a backpressure and iat like mnlx said. Even with the low timing you should still feel something with a 6lb boost increase. What turbo kit do you have?

Anthony

 

aeromotive A1000 75lb injectors cant remebrr ehat size line but its big enough.the heads are new maybe 500 miles.i was thinking back preddure but i was told cause all i have is the down pipe for exhaust that back pressure should not be a issue.as for IAT im not sure how i would even check that or the back pressure.compression ratiois 9:1

 

turbo kit was a treadstone but it been redone so i could run a bigger bov and wastegate.im running a 50mm JGS wastegate and a 56mm JGS bov...how would i check IAT and back pressure...

 

Backpressure doesn't just come from the downpipe, the exhaust housing has a lot to do with it also. Drill and tap a pressure gauge preturbine, like in the collector before the exhaust housing, have seen guys drill and tap the exhaust housing itself. The iat you could use a temperature gauge plumbed into the intake piping before the throttle body.

Anthony

 

why would i have a back pressure issue its a .96 A/R with the f1-68 turbine wheel...not trying to argure im just asking

 

Thats a small turbine for a 351, its going to have slightly high backpressure no matter what your downpipe is, when people talk about backpressure they are talking the pressure between the head and the turbo, in the header/exhaust manifold, not after the turbo, not the downpipe. Some backpressure is good, its what makes for quick spool, but it also makes stronger valve springs needed. Thats a fun turbo on a 351, spools quick, but you just have to be aware the back pressure might float your valves, sounds like that is what is happening possibly. Those stock vic jr springs might be pretty weak, they arent put on those heads with a turbo in mind. Look into the specs of those vs. what other sbf guys are using for springs.

 

i called turbonetics and thats the biggest turbine wheel they have in the 76mm or so thats what they told me.as for the springs is there a way i can test and see if its the springs

 

For a T76 or TC76 it is the biggest turbine wheel from Turbonetics, but it still has a fair amount of back pressure on a relatively big engine like you have. There is nothing wrong with that or with the turbo, it gives a quick spool, but almost any turbo setup has more back pressure than a naturally aspirated setup, so if you use springs that were spec'ed for a naturally aspirated setup, at some boost level your going to need stronger springs because the springs cant handle the back pressure from the turbo.

Lots of people run that exact same turbo on 6.0 LS engines, its the turbo on Turbonetics very own kit for the 6.2 Camaros, you just have to realize after a certain boost pressure you need stronger springs, not the turbos fault, its your springs fault. No big deal.

After typing all that out, it may not even be the valves floating! Just an idea, if I had to bet on the most likely culprit (assuming your not going lean as the boost goes up, look at your logs to verify) then I think it is probably your valves floating cuz your valve springs arent strong enough.

 

is there a way i can check for valve float? is it something when they have it on the dyno they can tell from the dyno or no.sorry so many questions i just dont want to waste money i already have more money in the car then i wanted to spend.lol

 

not going lean when we had it on the dyno while back A/F was 11.6 or 11.8 cant remember ill keep my eye on it tonight what would you count as being to lean that way ill look out for it tonight

 

Doesnt sound too lean at all, Im talking going way to lean like 13. Im not sure how to tell if the valves are floating for sure, hopefully some more people will give their opinions too. Look and see what other people are running for springs on turbo sbf. On the dyno the graph will flatten out and even have some drop outs sometimes with valve float, but sometimes people say that is a weak converter too. You might also make sure your ingition is up to snuff and your plug gap isnt too big, you could be having a hard time igniting the higher pressure of more boost. Too big spark plug gap will do this too. Thats free to try as well. Tighten your gap .005 or something and take it for a spin. Look at other peoples setups and see what gap they are running on turbo sbf as well.

We've all had :2g1c: like this go on, just part of doing turbo stuff, once you get it figured out though hang on!

 

my ingition is all msd msd dizzy,coil and msd digital 6 plus something like that.plugs are gaped i think .32 ill check tonight to make 100% sure what the A/f is DOING AT WOT

 

Good thing with this problem, if it runs good at 8# and not really any better at 14# or whatever, there are only so many things it can be. Make a list of everything and go through them, cheapest first

1. .032 might be a little big on the spark plug gap
2. Springs sound weak for that much boost
3. Converter could be crappy?
4. You ruled out going lean
5. IAT going way too high??

Probably a few other things

If you have alot more time than money, you might try shimming the springs a tiny bit to get more seat pressure, this is a bandaid fix though, make sure you dont get into coil bind. This would maybe tell you if its your springs without buying new springs yet. Beware of bind though!!!

 

also the convertor is from PTC 4000 stall seems real tight alot of people sid i would not like a c4 but i love it drives great on the street

 

If the valves have been floating long enough, there may be a witness mark on the valve stem.

 

What if you backed the boost off to say 12 psi and see how it runs?
you should notice good power increase even with slight increases in boost
with that engine.
Trying to jump 6 psi might be a little much especially if your having problems now.

I have less engine and when i went from 8 psi to 11 the car laid down. Found out it was my coil.
it would keep up at 8 all day long but not at 11. Felt like a rev limiter at about 4500 rpm.