sbcgenII

iTrader: (1)

What compression and timing? I have seen a Holley lay over around that rpm with a bad reluctor wheel or crank sensor.

RICE ETR

iTrader: (3)

I'm not sure what coils you are running but I know the recommendation on dwell went down from 4.5 to 3.5ms due to some of the coils auto firing (early/random). I believe the truck ones with the heat sinks are the main culprit.
I'm running mine at 3.5ms and 2ms spark duration fwiw. I know some run it at 2.5 and have no issues at 7,000+. Is you battery voltage staying at 13.6-.8v?
Car looks great

Forcefed86

iTrader: (4)

It’s a 241 (68cc) head on a flat top 5.3 with LS9 gaskets. So right around 9:1 I believe, maybe a hair less. Timing is goofy low by the end of the run. Was like 13* at 8lbs. Had a commanded 20* but the my IAT’s were pretty high at 208* by the end of the run. And that’s with 7gph of washer fluid sprayed into the inlet of each turbo. (no IC). It was pulling 7* by 200 which I probably hit the last 330 ft mark of the track. IAT is in the intake behind the TB. So maybe the fluid is mainly flashed by then. I was thinking it would report lower. Also seem to be sucking in 125* air when its 78* ambient. Need to block the engine bay heat from the turbo inlets better. Filters are in the fender wells 100%. Was thinking it would pull in cooler air than that.

I’m sure it’s way down on timing. As it picked up 7mph leaning it out a half point and raising timing 1 degree. (also shifting at 5800 vs 5400 ish). But I still feel like I should be able to rev it. My 370 feels the same way… Almost like it’s an ignition hardware/software thing and not engine related.

A lot of things to check. Still totally new to “hot air” builds. Just though it was weird every LS I’ve done basically falls on its *** around 6k. I can still get them to run pretty decent, but it seems way less than optimal way to do it. All the “fast” SBE guys are really rapping these suckers out.



It’s only the D-585 heatsink coils that will “auto fire” at higher dwells. These are the square truck coils. I bumped it to 4.5 and it made no difference. I have them at 4 above 100kp. It’s lower at idle and cruise. Battery is 13.9 steady through the run.

thanks!

svslow

What is the spool time like?

Forcefed86

iTrader: (4)

About 2.5psi by 4k loading it up on the foot brake. Pretty slow. Builds quite a bit on the trans brake, but the worn out LSD wasn't allowing any sort of hard launch.

Forcefed86

iTrader: (4)

If anyone wants/needs to see the whole build thread with working pictures you can see it here.

https://www.theturboforums.com/threa...-build.382086/

sbcgenII

iTrader: (1)

I would keep it rich since you are a hot air car. That way more fuel is going in the cylinders keeping it cool. Just keep adding timing and watching your plugs.

I would also make a pass without the outerwears and see what happens. I have had them mess up the jetting on a banshee before.

Are you monitoring fuel pressure? I dont remeber what injectors you were runing but your idc caught my eye.

Forcefed86

iTrader: (4)

It's around 11.5 till 5lbs or so then ramp it down to 10.8 range around 10lbs...

Fuel pressure is set at 58 with no boost reference at the moment. Logging pressure. Pressure dropped with boost as it should, but not excessively. Running deka 80's.

Even at 4-5lbs and a solid 20* it doesn't make power past 6k. Just feels dead up there. Feels great up to that point, then just falls on it's face. No breaking up, Does this without the water meth spraying and does it at 4-5lbs of boost as well. Guessing it's a software or IGN hardware thing.

svslow

I have not messed with Dwell times much but I took a look at what its my tune. I am using a fixed dwell of 3ms with 1ms spark duration. Doesn't seem to give me any trouble, using the same coils as you. Pulls great all the way to 7500.

stevieturbo

Pretty much every setup I've had, doesnt want to be above 6500 or so. Some will go to 7k or maybe a little further, but you just know they're not happy there.
This is despite various engines, ecu's, heads, cams, intakes etc.

Although dying at 6k just seems all wrong

I'd love to know why some guys have theirs pull strongly to 7k...7500 etc as I'd love to see mine peak around 7k. If I can get some money up and it will fit, I'd like to try Shearers new take on the dual plenum Hi Ram. I think it might just squeeze in to my car.

Forcefed86

iTrader: (4)

What makes me think it’s tune/software related is the fact that all my MS3 setups have done it. Tried new coils, plug gaps, wires etc. Tried different push rod lengths (the correct lengths VS slightly short and long) Nothing seems to make a difference. Rx7 pulls very strong to 6k pushing 8.70 quarters at 160. The mustang feels very similar on a smaller scale. Nice strong pull to 5800ish… then starts to lay over and feels like its making NA power levels by 6k. It’s nice and smooth, no breaking up that would indicate fuel/spark related issues I can tell. 100% factory valve train with .660 BTR dual springs. It is only a .525 lift cam so I should shim these springs a ton. But I am aware of several guys running them un shimmed on similar mild cams pushing well over 6k. Not looking for a competition dragger here… tired of blowing money on aftermarket valve train parts that never do a thing to help. Picked up these heads with the springs already installed for $200 or I would have went with a 1218 or similar.

ls3fox

what intake are you running if its a truck intake maybe thats why ? just a thought

Forcefed86

iTrader: (4)

It’s a TBSS truck intake. LS6 on the Rx-7. Both factory intakes have made great power well past 5800. Even the older gen3 truck intakes pull strong up to 7k. Might not be ideal, but should still maintain power in the upper range.

stevieturbo

I would be amazed if there was anything to do with the ecu that would hold it back above 6k.

It would need to be screwing with timing or something really although that might show up at the plugs or EGT's if it was ?

LS2 67GTO

iTrader: (8)

My 5.3L seems to do the same thing. On the dyno power drops pretty quick after 5800. I'm running MS3 with a S475 T6 1.32 with a fender exit exhaust. Same springs and a Martin spec'd cam. Would like it to pull harder up to at least 6500. I havent tried changing dwell settings and I can't remember where I'm at. Maybe I will give that a try?

Forcefed86

iTrader: (4)

Really don't thiink dwell will do a darn thing. I'd look elsewhere. Wish I knew where to point you.

Nitroused383

iTrader: (10)

I would guess most of the time if you're running stock lifters with heavy springs you're bleeding down lift and duration at high rpm. That to me seems to be the most common issue with some setups not revving. I've seen some back to back swaps with quality lifters that pickup alot of hp over 6500 rpm.

purple73

Hello forcefed i really get alot out of your builds. Ihave a very similar setup as you and it was laying over at 6000 ish when afr under 11.0 Leaning it out helped it rev clean to 7200.

Forcefed86

iTrader: (4)

The springs installed now are only 155 closed and 400 open. The 400 open will actually be much less at .525 lift since the springs are rated at .660 lift. I was actually wondering if the BTR springs are not supplying enough pressure at .525 lift. Anyone happen to have a 660 BTR spring they could test at .525?

I really want to get away from tearing into motors and replacing hard parts. Seems like I get those suggestions a lot. I always jump right to push rod length, and bigger springs. I’ve yet to have those parts make any difference on any of my builds. (not that hard parts can’t fail). Capazzi and several others are running stock lifters with more spring over 8000 rpm on factory lifters and rockers. Unless the OEM parts are damaged or worn out, I can’t see them being the issue at 5800-6800 rpm which is all I’m really looking for. Just want to check all my free options first. Seems like it’s usually something simple/stupid on my part.

Thanks for the input. Was that on E85 as well? I’ve been in a lot of over fueled turbo cars and they usually miss/sputter etc. With E85 I really don’t’ think my AFR is that rich. Esp. for a hot air car. With the boost down to 4lbs I tried up 11.5-12.0 and it made no difference RPM wise.

jimmyg

If u use an I pad or I phone , you can load pics directly from device to the thread. Tap the icon that looks like a postcard with mountains on it.