Detonation potential is not gone by any stretch of the imagination but it's certainly alot more difficult than pump gas. I know this is just an opinion but I wouldn't have any problem throwing 2 degrees in and see what happens with that fuel and if IATs aren't extremely high. If it makes a big difference put another couple in.

 

No offense to CX racing, but it sounds like they don’t have a clue. You can’t say “X” turbo is good for 600hp on every engine. Because that turbo is capable of 600hp on a 2.0, doesn’t mean it’s capable of 600HP on a 6.3 liter. They can’t maintain the same inlet/outlet pressure ratios on the larger engines. This puts them at an inefficient island on the compressor map.

I’ve been told by several turbo vendors that a 1.0AR T4 is smaller than a 1.0AR T6. Which would mean a .8X T3 is TINY. When I ask the actual diameters no one ever seems to know. I read over on yellow bullet that a 1.32 AR T6 housing has a 1.6” exit diameter per volute side. That’s 1.6” diameter per exhaust bank plus the restriction of the wheel.

I’d assume a .8x T3 has a super tiny volute exit diameter. Either your back pressure is building up to excessive levels and “bottle necking”, or those turbos are just out of steam on your engine, basically out of their efficient operating zone. (or a little of both).

If your back pressure levels are high, coupled with a high overlap cam you're pushing alot of hot exhaust into your cylinders. Race fuel or not, you can still detonate in situations like this.

 

I agree with this ^^

 

i'll check the backpressure, i had welded a bung in the collector to check it on the old motor, which showed 25 psi backpressure(it was fluctuating quite a bit on the guage) at 15 psi boost. i thought a 2:1 pressure ratio wasn't bad?

 

What all has changed with the new setup? 2:1 is pretty good, but your cam also has 16* of overlap in it. I shoot for neg overlap @ .050 with street turbo setups.

 

The old engine was 244/254 bullet reground it to 244/244. New engine has reground cam bigger turbos and 3" open exhaust instead of 2.5". That's kinda why I'd be surprised if it was out of turbo

 

And the turbos may be fine... Just throwing out ideas. We are all just guessing without more information.

Do you have a WB02 and log your AFR? Assuming the plugs look good?

Here are the turbo specs for anyone else interested... They look pretty good to me. I think I may have even suggested them awhile back.

 

haven't logged widebands, and i put a second one in on the other bank that is totally independent of the first to be safe, numbers range from 11.6-11.8 . i appreciate all of the help! car runs fantastic for what it is, i know the weight is a big problem to go any faster, i'd like to see a high 9 pass and i think i'd be satisfied!

 

Not back pressure, not afr issue, try to go back and turn the rpms higher, plus add some timing to it. See if it picks up.

 

I'll find out Sunday heading to Orlando

 

If it was me I wouldn't go to the track I would go to a dyno.
You have a lot of possible issues and taking the car to the track or pulling on it in the road to me is a waste of time at this point. To much crap to worry about at the truck plus how many runs can you get on track day. Find a good shop that can tune turbo cars and book an appointment. I few pulls on the dyno with a good tuner can start point out issues and if they can be fixed or tuned you can start eleminating possible issues.

Dyno graph can tell a lot pluss it doesn't allow for a million variables like at the track.

I didnt want to spend money for dyno time but it helped me sort out my combo and I could pull on it as hard as I needed to and could keep an eye on stuff and shut it down if something didn't look right.
[video=youtube_share;VJgJ2Wlfq-0]http://youtu.be/VJgJ2Wlfq-0[/video]

 

its hard around here to get a dyno guy to want to run the car, being turbo and carbureted. one jackass near hear told me that if it doesn't have a plug for him to attach his laptop to, he wouldn't work on it! the other guy will only do naturally aspirated. i'd have to go to jacksonville(5 hour drive) and see tony from tuners inc, who is fantastic, and i just don't have the time. if we can't get it to run rite tomorrow then i'll have to take a trip up to jacksonville. i have a couple of friends coming tomorrow to help that are good at tuning cars so hopefully we can sort it out.

 

ended up running the car, found same thing, best run 10.20 . increased timing, no gain, spark plug readings all good. next thing i'll check is the valve springs. what is the life span of a set of springs?

 

what brand and part number on springs
basic cam specs again s
olid roller hydraulic roller

FWIW

if the cam and springs are closely matched and they are not of a good material then they may not live as long.
also a spring that is closely matched for a N/A ap may not live as long on a boosted ap because they have to work a lil harder.
also because of variable when building engines, spring set up is key as well ie spring and install heights.

 

I'd think you could hear valve float and it would nose over hard in the upper RPM if it were springs. were your springs matched to your cam?

If he is monitoring neither, how can you assume the above? If it’s not making additional power per lb of boost at lower RPM, more RPM will make it worse. Throw a tire pressure gauge with peak reset on a coil of copper wire and tap each hot-side. It’s a hour job at most and under $25 worth of parts. It’s also great information to have down the road regardless.

 

That was my original assumption. I even posted earlier in this thread abt the turbos being too small. Especially its on a t3 footprint. Plus an small 62mm turbine wheels on a 383 cu engine. I wouldnt put a t3 twin on my little 306. I can't imagine a 383 with a solid roller.
Problem is he's also shifting the car at 6200, I have a lot smaller hydro cam on my 306 and I shift at 71-7200. It might be all three, back pressure, small t3 turbine turbos, and valve springs. I personally think its the turbos.
To the op, when you went testing, did your try to shift at a higher rpm? Say 6800? Does the motor even let you rev higher?

 

I just looked in my notes springs are 3 plus years old and were purchased/set up by the machinist,I gave him the comp cams spring recommendations. Since then the cam was reground by bullet. The heads/ springs have probably 15-20 k street miles and at least 40 passes on them. Machinist never asked about boost pressure. It is a solid roller. I tried once to wind it past 6 k on the street manually shifting it and it seemed like it really didn't want to pull past 6200 and revved but just made noise without pulling. The only header pressure reference I have is from the old engine with smaller turbos and it was 25 psi exhaust 15 psi boost

 

Try running it to 5500 rpm and upping the boost.

 

Its not all that uncommon for springs to act like the op is describing... no typical signs of float, but power just levels off. More boost, and drive pressure will only make the problem worse. If has been in valve float for a long enough period of time, there may be witness marks on the valve stems.

 

Also, there were a few of us who tried to talk the op into t4, and P trim sized turbines, but he had some drive pressure info that looked like these turbos wouldn't be all that bad. I believe his cam was spec'd after the turbos were chosen, but 244 @ .050 in a solid and 6200 rpm in 383 ci doesn't sound too far off to me. Its tough to compare a hyd to a solid with almost 80 cid difference...