Chuck from HPE came out to Utah yesterday to do a group tune. My computer is pretty much maxed out at 4600 rpms so we couldn't run it up any higher but here are the results.

http://www.youtube.com/watch?v=AcX8s2YI_rQ

 

very nice, so you need a new pcm and then a new tune ? How much boost ?

 

Thats what it sounds like. Its hitting about 13psi when its freakin out at 4600 but we did run it up to 6 grand and it was 18-19psi.

 

Thats not your computer causing that. You need to look elsewhere. I'd be really concerned about spark blow out. Thats kinda what that looks like. You also didn't say what your A/F was and it's hard to figure it out on your dyno chart, but if thats your true A/F read out, you definitly don't want it going up through your pull. That means your not adding enough fuel in your tune, or your out of fuel system and not supplying enough. Never the less, look elsewhere besides your computer. There's plenty of guys out there making more power then that with the factory pcm. Hope the info helps ya out. Has the potential to make good power all the way though.

Ken R.

 

Boost is climbing upwards of about 13psi when the graph goes crazy but the few times he took it to 6000 it got up to 18-19psi.

How do you determine the spark blowing out? He had the wideband for the dyno hooked into all his stuff he was tuning with so I don't know exactly what it was at. He said its still pretty fat up until the graph freaks out then it goes really rich then spikes to lean. We hooked up a fuel pressure guage and pressure was holding fine.

He made 14 pulls trying to fix it and he said the VE and power enrichment tables are maxed out and he can't add anything more at that point and he said its pretty much at the limits of the stock pcm?

 

Unless you've already done it, by gapping the plugs to .032 and seeing if that dip goes away. What is your current gap? Are your springs spec'd out to work with that PSI? Some guys are running enough psi that the valves won't stay closed because their valve springs aren't strong enough. Great numbers considering it's a 'tainted' run! I didn't know Chuck tuned LT1's .
HPE isn't that far from where I'm working here in Houston (on contract).

 

Ya, I don't think Chuck was very excited to dive into my car lol
My current gap is .032 on tr6's
I have never really thought of it so now that you mentioned it I looked up what valve springs i'm running. I had speed inc. build me a long block and they got my heads from scoggin dickey which are listed as LT4 CNC ported version 2 assembled and all it says about valve springs is diameter-1.320" and max lift-.525"
As far as I know thats what i'm running. I guess I better find out for sure!

 

For the plugs, your gap is good. A lot run the TR6's here, but i prefer a non-projected tip plug. I had spark blow out even though i was running a .030 gap, but a projected tip plug. Got rid of it by just swapping to a non-projected tip plug. I usually run the NGK BR7EF's or Autolite AR47x, with the x being the heat range.
.525 is not a lot for max lift. What cam and rocker ratio are you running? You also need to know that A/F ratio. Although the pressure holding steady isn't a bad thing, pressure kinda means nothing in an application like yours. You can have pressure holding, but you may not have enough fuel volume to support the power. You should also have a boost referenced regulator on your setup too. That way, fuel pressure will step up when boost steps up.
As far as the tune maxing out, if your running a MAF setup (are you or speed density), then MAF readings will max out under that much boost. Doesn't mean that you can't continue to add fuel by RPM. Now if he's maxing out the PE tables to try and get you more fuel, then that means your out of fuel system and the engine isn't getting enough fuel, in which case, it would be time to upgrade. With your numbers, i'd say you should be looking at a dual high volume 255 in tank setup if you don't have that already, and paralleling your fuel rails would also help greatly. Larger fuel lines would also be an improvement and give you plenty of room to grow if you choose down the road. 60lb an hour high Z injectors at a minimum would be needed as well although Racetronix is making a 72hr high Z now i believe which would be even better.

Ken R.

 

The springs were something my cam grinder (Bret Baeur) was very particular about. He wanted to know rocker ratio, PSI, what RPM I'd be rev'ing to, what kind of valves I was running(weight/stem length). With all that, he was able to arrive at a spring, retainer, lock configuration that would be 'just' strong enough to control the valve but not provide so much over what was required that I'd suffer extra frictional losses. I don't know for sure but those springs almost sound like standard sodium filled LT4 valves related springs. If so, those are too light weight for anything other than the LT4 valves for which they were designed. I'll see if I can find my springs/retainers (Beehives) for my cam and I'll post it here just in case you want to have a look at them. My cam has a little bit better than .550 lift with my ProMag 1.6 rockers.

 

The cam is 216/222 .560 114lsa with 1.6 pro mags.
I have always read the stock regulator is boost referenced, thats why we hooked up the fuel pressure guage and it did increase with boost.
For the first few pulls we were running with the maf but he switched it over to speed density to try and fix the problem but never could.
I am running dual walbro's and 60lb/hr injectors and stock lines, regulator and rails.
I checked my reciepts and they say nothing about the springs so I emailed speed inc but they lost all their records prior to about 06 so as far as I know I just have stock lt4 valves/springs.

 

Ok I just found out what I have:
comp cams 987 springs/4771 seats/740 retainers

 

Without raining on your parade of problems, just want to say those are some nice numbers 650/720 with more left in the LTx

Congratz on the increase from your last set of numbers ! I can't wait to see what it puts down when you get the details iron'd out

 

What does tire spin look like on a dyno chart?

How does the car drive? Do you believe the graph?

How does the wideband look?

Just a question here, but PE tables maxed beyond 650HP@4600rpm. Somebody please tell me that fuel is not the problem. What are you running for spark?

 

Thanks guys! I don't know how to spot tire spin on a graph? I got on the car on the street but only ran it up to 4 grand and it felt incredible!

 

Do you know what the seat and full lift spring pressures are supposed to be and at what installed height? Maybe it is only wheel spin like he said. If you're fuel pressure is stable and high enough, it doesn't seem like you're running out of fuel. Dunno. Our 60 pounders are supposed to be good to 600ish at 85% duty cycle but I don't know if that's at the crank or at the wheel.
In the end, as long as it's safe, engine wise, and you're having fun, the dyno numbers don't really mean that much. So many things can affect those numbers. I wish you and I were geographically close. It sounds like it would be a fun race between us.