I have all of my limiters maxed out as far as I can tell but the car still hits a wall right at 6500 rpm. Just seeing if anyone sees something I missed or if it may be a mechanical issue. Attached is the Tune I was running last night and the log that shows the limiter.
24 degrees pull.hpl
JAMES C5 V0030 AC TORQUE OFF.hpt
Maybe someone can find something, do you have a wideband? Seems that it is leaning out towards the end of that gear. You can watch InjPW start to lower, whether that is a limiter or the MAF isnt dialed in around that area.
What was all done to the engine? Doesnt seem fuel pump related being the IDC doesnt sky rocket, but it is always good to verify.
I would look real close at valve springs.
MAF noses over at 6300. It looks like an airflow issue. What intake manifold, t-body, CAI? Looks like a healthy 408 with a stock LS1 throttle body.
It's not tune related it's mechanical. The engine peaks then noses over.
Also could be valve springs.
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Engine is 11.4:1. BTR 400+ camshaft. Stock LS6 intake, Stock TB, Vararam CAI. I have a wideband but it keeps disconnecting from my scanner. I've peeked at it while on the throttle and the AFR always looks good. A little on the rich side but plenty safe. 11.4-12.0. I didn't imagine that I was just at the limit of the TB. I left that stock for now figuring it would be easier to get the tune going.
Something can't keep up.
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I doubt it would be the TB, being the MAP doesnt tank when RPM is tanking. What heads and valvesprings?
PRC 237cc cathedral heads with their supplied .660 springs.
As far as AFR, i just didnt like how one of your O2's are going lean at the end, that could also be the archaic scanner delay. Vettes arent bad to pull a valve cover. Id maybe look at the springs inner/outer.
So PRC knows which springs that cam needs to go +6500 with heavy-ass stainless valves?
Is there a part number or something more than "BTR 400+", or is this just how the world works now?
Other things...
What is the crankshaft end play?
Is the crank sensor OE GM or some parts store offshore garbage?
When it reaches the 6500 limit, what does it sound like? Like a traditional rev limiter?
I bought the long block out of another car that was being parted out. Engine builder said it was put together to turn 7500-8000 rpm. The car before was using nitrous and shifting over 7k rpm. The engine had a nitrous cam in it but I don't plan on spraying it so I called BTR and went with the cam they suggested. End play is fine, the whole build has less than 4k miles on it. It is a Gen 4 rotating assembly that I am using the Lingenfelter Crank and Cam conversion box on. I'm going to try to get my wideband working on the scanner today I don't know why it it being a pain lately.
Here is the Link to my cam. Doesnt look like they really use Part numbers over there.
https://briantooleyracing.com/btr-40...mshaft-v2.html
Everything BTR grinds for cams will work with your average .650 or .660 LS spring.
Nothing with a plastic stock intake is going to pull to 7500.
Valve train is the 2nd biggie when it comes to RPM. A mild "stage 2" type cam, won't pull to 7500.
As for it NOT being the throttle body, yeah I can see where the MAP not tanking would lead you to believe that. I'd agree in most cases.
This one is a little odd. The MAP actually has a bit of a bump in it as it starts to nose over.
To the OP, what is the exhaust configuration? Can you describe the layout?
I'd be inclined to lean on it and see what it does. I've had "built" engines I did not know all the specs on, nose over like that with not enough timing in them. I'd set them up with the normal for stock compression, and they'd end up taking, in some cases, WAY more than normal because someone screwed up on the compression calculation.
Had a built, blown combo years ago that took so much timing, the wheel had to be installed wrong. I could not believe the amount of timing it took just to clean it up, not to mention making power. I told the owner something had to be wrong with it mechanically and I would not run it as is. It ended up making over 700 wheel, but the timing was ridiculously high.
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'Everything is basically new' means it all HAS to be good, right?
236/250-whatever is more than enough to go past 7500... with the right springs. I'm not sure a generic ".660 lift" spring with 140 seat/400 open is going to be up to the task though. The LS6 intake is hurting it but that won't make it behave as if it's hitting a hard limiter - but valve float sure will.
BTR 400+NA CAMSHAFT V2
236/25X, .636"/.636", 114 LSA
Exhaust is American Racing 1-7/8 longtubes Catless with matching X-Pipe and mid pipes. No Mufflers as of yet.
I changed the engine because the last one injested water. Just removed the TB and removed the motor from the housing and it was pretty gunked up where water must have entered it. The blade was hard to operate with no motor on it. I think it just wasn't opening all the way. I also had a high idle issue so im thinking everything has to do with the blade not moving freely. I'm going to look for a good intake and TB for my setup locally right now.
If this is the typical ".660" dual spring with coil bind at 1.080, and your installed height is the typical 1.800, you should have enough space to add a .060" shim without binding. That would raise the seat pressure to 165-170, and if that doesn't show a very definitive change in where the 'limiter' kicks in you can rule out the springs and move on to other less obvious things.
Lingenfelter Crank and Cam conversion box.
Please don't say that haha.
Well you're going to have to start checking and testing things, this isn't going to be fixed with a keyboard.
I understand that. I've got the tune pretty well dialed in. Finally got my wideband on the scanner yesterday. Tried turning off my 2 step module, that made no difference, have more timing in it, fuel does not lean out, throttle body is fixed and working like it should, "limit" is still the same. I'm going to drive it for a little while since I've been waiting so long and just shift at 6k of I go racing. I'm getting a new shop next month and when I get in there I'll start taking it back apart.
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