Ls1 (D1SC Frankenstein blower running 4.63 pulley and 7.65 crank)

PRC225 heads 62cc chambers
235/243|.630/.615|111LSA.
LS6 intake,
60#Dekas fed by 340racetronix through vette style setup.
10GPH meth running boost juice(49/51) at the moment
br7 plugs gapped about .025
car makes 8-9PSI at 6200rpm, meth on at 3 and max at 5.
Making positive KPA at nearly all rpms under WOT(

car is breaking up at medium lower rpm(2500) under a bit heavier throttle and also when holding a gear at medium rpm with low throttle, I.E. rolling 3200rpm in 2nd. Most noticeable at light loads and medium rpm but noticed slight hiccups sometimes at 2500. If you hit WOT at any rpm there is no bog or stumble. Pulls very well. 85%IDC commanding 11:1 AFR with methanol supplementation.
it was worse before and I pulled the br7s and changed from their stock box gap to .025/.024. Sounds like first step is I need to go even tighter on the gap? .022 or .020?
God if I could only remember for sure, it’s definitely still smoother than the stock box plug gaps but I feel like it may have been a good bit better when I first installed the regapped plugs…possible fouling issues along with the gap? I have a fresh set of br7EF plugs ordered and will have them tomorrow.
I can post the tune and several logs. Car acts the same open loop or closed, that being said I didn’t see anything super alarming in the fueling but then again I’m more of a tooner. Timing is very conservative in boost regions and likely could be pushed 3 or 4 degrees farther.
STFTs are typically +\- 1 or 2 as long as dfco is off and AFR VE is nothing but a little fat at higher rpms.

anyones input on where to start or their experience with how finicky these plug gaps can be would be greatly appreciated. This car ran excellent NA with heat range 6s not even 1k miles ago..so I think it’s either in the plugs, or the tune.

 

logs and tune. Am wanting to lean out WOT and begin to push timing as I get issues ironed out, as of right now averaging between 11 and 10.7 between 3.6 and 5.6 rpm and 11.0 from 5600 to limiter with not much spark in it. Right now it drives fairly well, bucks every once in a while in low rpm. Cant get decel to lean out right so DFCO eats most of that up.

 

I'd start with fresh plugs. Gap shouldn't be a huge concern at low rpm, no boost. Its under boost that the smaller gap is needed to prevent blowout.
If the fresh plugs fix it, figure out why it fouled these

-you sure its not spraying Meth when it shouldn't be/doesn't need to be?

 

Why are you running 10.7:1 AFR?

That's not helping....anything...

 

On tuning this 2 bar OS with this NA cam I definitely miss my MAF sensor., I’d have to look at logs again but I think car is capable of starting to build boost at 2000rpm, and with the low vacuum producing cam it is possible it’s closing the bypass and pressuring the intake even when it is at low tps. If I recall I’ve seen 100+KPA at low throttle when around 3,000rpm.

Bob from brute speed seems to suggest someone swapped tags over from an f1 unit as this is the biggest pulley I can run(had to cut a hole out of pulley flange for procharger bolt).… and he would have expected much less PSI with the better flowing heads and inefficient NA cam.

Also, I’m sure meth isn’t being commanded during this situation. it’s commanded to be 11.0 under boost while spraying a substantial amount of meth.. I plan on further dialing in WOT and starting to push timing up but I’d like to get rid of these missing issues. The plans were to just leave it tuned for 11.0 on the meth, since if meth were to fail it would hopefully stay alive, then again it probably won’t, car made 450 wheel NA so it’s likely to be making some cyl pressure/heat with 8-9PSI on what I was told was a SBE
..
So start with fresh plugs, gapped the same and see if it clears up? If so then gonna have to figure out the fouling. Not sure how to really combat that if that’s the case besides running a hotter plug, would pushing timing up at idle help these clean off?

 

Your rich and dumping in the added meth/water will bog it down. When does the meth kick in and is it 100% shot or on a progressive controller? I would
get a bog and breakup when my meth hit all at once and I have since moved to a progressive
controller. You should also not be leaner than 11.5 at min and with all the meth ur dumping you could be 12:1 and not hurt anything. I also don’t run the br7 on light boost and prefer TR6 which I run at basically
0.28 gap up to 15psi and I spray 70/30 mix progressively really early in a turbo application.

also what coils are you running? Look at timing and fuel around the breakup area.

 

I’ve always seen 11.0 to be touted as a safe AFR under boost. It is tuned to be 11.0 while under methanol. So I’d guess it would be high 11s if it isn’t spraying or more. Purging the pump while driving drops AFR from stoich to 12.5. It isn’t breaking up at all under WOT. Meth is on a progressive with a rather fast ramp rate. Start at 3 PSI max at 5 and I get zero bog from it, however the cam really gets into its meat and potatoes at mid to high 4K so it’s more or less under full methanol injection at peak torque.

When it’s breaking up it’s not into boost, without the logs in front of me I can’t be sure but I think it is at near atmospheric KPA at pretty much any throttle required to hold rpm
above 3,000rpm. I assume the excessive overlap of this cam always riding high on the KPA doesn’t help that much.(it always made tuning it a PITA as I have low resolution on the lower rpm side of the VE table)

running stock coils and msd wires
I really want to get these 7 plugs to work, trying to keep as much heat out of the cylinders as possible. Again, it was a great running NA car with the 6’s and currently it runs great under WOT and cruising around but if you were to say try to roll race it stumbles holding rpm.

so first step would be pulling the plugs and leaning out the WOT AFR to Atleast 11.5 under methanol? I don’t ever plan to not have methanol on this car. In all reality I could probably just lean it out and remove the fueling fallback, if the meth fails it would really be likely it would scatter it regardless. I feel it’s on borrowed time pushing it this far but it’s only gotta hold it together for this year. The plan was to get 5ish PSI for the shakedown and drop to the recommended pulley by Bob. But turns out it made 3-4 PSI than anticipated. I guess me being such a conservative saved the motor. Wouldn’t be a stretch to say it would’ve made 11-12psi with a 4.3” pulley…
sorry for long responses lol. Seems to be a bad habit of mine.

 

Pulled from cyl 5.

 

Is it intercooled?

At that boost on pump gas I'd run 11.5:1 AFR or .78 lambda.

My guess is you are drowning out the plugs which is causing it to break up.

 

Happening while not under boost. Motor has about 11:1 compression. Supposedly SBE motor... I’ve read many threads before hand and gathered 11.0 to be a good safe AFR for a SBE setup like mine, is that not the case?. Spraying meth on top is more for protection and to cool the cyls. Has twin 4.5 intercoolers from procharger..plugs look fine to me. Spouses friends are over. Soooo going to change them anyway to avoid all those mid twenties women and their white claws

 

11:1 is too rich. I would break up at high 10s. Your 50/50 meth is adding probably .5 to that bringing you down even more. Realizing this is out of boost your motor is going rich on the transition as MAP increases so your NA 13.5 going down to 12.5 down to 11:1. Im not looking at your logs but your you should be starting boost or in a psi or so by 2500 which means your in the 105+ KPA area so look at the fueling there. Your boost is low and I would run a hotter plug. Being intercooled and spraying 50/50 is a lot of protection. A 70/30 mix like wiper fluid would give you more protection with higher water and the lower meth will reduce the hit to the AFR.

Lean it out a bit and see if it improves. I would also stretch out the meth progression and start it a bit later say 4-5psi and full in by 7 or so. You. An tighten up the plugs if you want but I don’t think that’s your issue. I think it’s fuel honestly.

 

Car made mid 400s NA when it had the 10 bolt rear and is now having 8-9 psi through it. I don’t think a 6 heat range would be the move on it would it? It’s likely it would cure it but from the information I’ve leached from this site, it should have the br7s…
it’s not under boost when this is happening, just at 90-100 kpa, if I go WOT from 1600rpm and put it into boost it does not happen at all through the entire rpm range. If it’s stumbling I can stab the gas and it pulls right along. It’s only light partial throttle to maintain rpm or to gradually climb rpm while holding a lower gear.. it’s not commanding PE or BE when it’s happening, its commanding and maintaining 14.63 stoich, unless I’m misunderstanding what you’re meaning…
one thing I just thought about, I ramped timing down to meet the low timing under boost, possible I’ve over done it and it needs more advance in these areas?

 

timing would make a difference. Plug heat range has nothing to do with how much power your making. I’m running TR6 and I’m running 6 more psi than you and maxing out 72lb injectors. Heat range is about heat in the cylinder and your at relatively low boost. Leave the 7s if you think that’s best but I would richer up that cruise area if your commanding that lean and play with the timing. I also think ur in the 6 heat range but seems everyone jumps from stock to the 7s but I like the 6s.

 

i was on the TR6s gapped .050(if I remember)while heads/cammed. car ran good and liked them.

Just compared timing tables, with the blending im only .24 degrees less in the area it’s missing than I had in the NA table…as far as I know plug heat range has to do with how much heat your putting into the cylinder. not just boost numbers. More power is what makes heat and cyl pressure isn’t it? From what I understand of it, More boost goes hand in hand with power typically but 10PSI on a 8.5:1 motor is a hellova lot less heat than 10PSI on the same motor at 12:1…
I too have maxed out the dekas with the meth . What injectors do you have? As far as I know we likely have the same sized injector..I’m at 85%duty cycle atm. However im not boost referenced so there’s a tad more left in them, I wouldn’t think very much. They are only fighting a hair over half a bar of pressure lol. I might still have my TR6s somewhere when I pulled them. Tempted to regap em and try it

 

my 5.3 has decked heads so compression is closer to 10:1. I run FIC Bosch 60lb at 43psi and I run them boost referenced at 58psi and a 450lph intank. Yes heat in the cylinder which is what boost is, hot air plus increased cylinder pressure and more fuel in the same space. Most people who put bigger cams
actually reduce cylinder pressure which in turn reduces temps (depending on the cam specs). I’m only saying that 10psi is not a lot of boost on a LS with aluminum heads and yours is a 5.7 so prob also an aluminum block. Which reduces heat in the chamber as well. Plus your taking a a lot out with the water meth. I think your plugs are too cold even if it doesn’t fix your problem. If you were running 15+ psi I would tell you 7s on the plug but 10psi is a smidge up over baby boost. I mean most older motors ran 4-6psi and didn’t touch the plugs or timing and just added a FMU in the old kits.

FYI this same motor I ran a torqstorm centri at 12psi with the same setup (plugs, gap, gas and meth) and never skipped a beat.

if it really is commanding 14.6:1 and your out of boost and the meth isn’t on and the timing is ok then add a bit of fuel and see what happens. When u gun it your adding fuel and air and I doubt it needs more air at that lean a AFR. I would also make sure your WB02 is working correctly as I don’t know what you got.

 

Ah yes my dekas are also 60# at 3 bar…idk I really was trying to get these to work, seems they are the go to for boost, non projected tip etc etc etc. oodles of people run these in damn near stock motors on the bottle and have no issues so idk wtf is up..wideband is so so at lower rpm but at 3k rpm the cam reversion is more than washed out and it reads true along with the STFTs, closed loop shows rich or lean by 1-2% and wideband hovers around the 14.63 area.

I got all the plugs out, they looked pretty good. would tightening or opening the gap up have any negligible effect you think?


What gets me is this is basically an NA problem right now. When I get it to settle down the Wideband and fuel trims aren’t showing much error at all so I’m lost where to go on the tuning side.

 

your gaps seem pretty tight for such low boost. I think you could open them up. Or throw those TR6s back in.

So whats changed from your previous combo to this? Fueling, plugs and the supercharger? Do you run a BOV and is it open at idle or on light throttle? If it was be I would be stuffing the TR6s back in and richening up in the cruise area like 14:1. Gotta give what the motor wants now what you want it to have. You should the plugs and added fueling should be a noticeable difference hopefully for the better.

 

Yes I just put them in at out the box gap, about .028”.(tried these initially and it ran like shat but some of that was my own error) What just came out was around a .024. As of right now I have 2 sets of these. I’ll clean the ones on the bench off and regap if need be.

yes 340pump, 60#ers and procharger. Procharger uses a bypass valve with a vac reference. Basically 100kpa and it’s closed. Lotsa vacuum and the blower is essentially a giant leaf blower blowing most of the air right out the valve lol. Blows dust from under the car at idle.

EDIT: I’ll also be hosing the tr6’s down with brake clean and getting them ready to go.

 

your getting to the max capabilities of that 340 pump by the way. If it’s a aeromotive stealth they are gone good for 90psi and flow drops like a rock around 70psi.

yea I call that the street sweeper noise and I hated it lol. Hence why I’m turbo now. You can put a higher spring pressure and close it at idle even tho that’s not the traditional way and I didn’t notice any surge. Made it more fun on thr street since boost was basically always there vs having to close the BOV and build pressure.

do you have another set of coils to test? Might just be a wonky coil but not sure why it wouldn’t continue throughout the RPM then.

 

Yea I know I’m pushing that pump and all. I’m thinking I’m really pushing the SBE. Originally life expectancy when going with the blower was probably just for a year lol. However my motors guts are questionable, PO who had it as a rebuilt cars/coffee cam only driver. He was a former instructor at some technical institute up in PA had it rebuilt in his class. had some pretty cool pics of the car in class having the body pulled etc…said the wife wanted an auto car so she could drive so he bought an identical one with an auto and was selling the m6 f body…was an older guy and I guess really had a thing for these ws6s.

Either way, I have long expected it to shat the bed, always been ripped on anytime I’ve had it out but 30k miles later, 7k rpm limiter with some money shifts along the way and here she is now still piston slapping like a forged motor since the day I got it.. The plan is run it till it drops and buy a shortblock and redo the fuel system etc and see what it does.
besides this damn miss and now it’s 95degrees out the AC overheats the car in traffic it runs very well. My brother calls it the mad max mobile lmao. Gotta do some searching and see how people wire the spal 16”&9” fan combo. New plugs didn’t have any effect on the miss.