I pulled from A2A I/C and went with the MeOH injection. Everything seemed to be fine, until I started pushing past 5000 RPM and seeing boost in the 18+ psi range and lots of drop in power and what seemed like "hitting the rev limiter". I was running dual nozzles (625 and 375) and I thought it was too much alcohol.

I ordered up the 275 nozzle to play with lower flows. However, upon talking to a guy that seems to be quite knowledgable on boosted applications, he said that it is not to much alcohol, but too much spark gap.

He commented that before I was running 7 psi at 5400 RPM and fairly high inlet temps. I am now running more boost (18+ at the same RPM), a denser charge (due to the somewhat cooler IATs), and also placing water in the combustion chamber. He commented that I have not slightly increased the combustion chamber psi, but dramatically increased the combuston chamber psi. He commented that as little as 0.001" change in gap can cause the spark to be blown out in high boost applications.

I told him I was running 0.036" side gaps. He said he would have expected a combo like mine to "need" somewhere between 0.029 - 0.032" gap.

What are you guys thoughts? Have any of you had to close your gaps for higher boost?

Thanks in advance,
Aaron

 

Aaron, in a word YES. I had to close the gaps on a former boosted car that I used to own. It was a mustang but same theory applys. I was up in the 16PSI range with a T trim on a head/cam/intake 306 and it would blow the spark out if the gap was anywhere over .035. And that was even with an MSD.

 

Lee,
When it blew the spark out, did it feel like it was "banging out" and power dropped dramitically? Mine seems to do it between 5000-5500. And prior to these changes it had no issues pulling past 6500.

Thanks for the feedback,
Aaron

 

From a racing friend of mine who runs a Ford 306 D1SC 8.75 comp with a roller cam in the .550" range runs 12psi wtih I/C. He had to close the gap on his plugs to stop detonation at higher rpms near the traps. At the end of the 1/4 or 1000ft mark he always had some detonation problems even with cold plugs.(don't know plugs range,sorry)But he swapped a new set,then closed the gap .010 and ran same gas as always and doesn't ping/detonate anymore.

I remember he stated he had to close the gap .010" from .035"! He was playing with gap before but never thought he'd go that low in gap. I know his ignition is a MSD Billet dist./wires and I think its a Digital style MSD ignition with built in boost retard.

I don't know if this helps any Aaron but gap did help a fellow procharged racer of mine.

 

Mine blew out at .035 @ 15 lbs.
Dropped it to .029 and everything was golden

 

Based on all of the comments above, it seems that I will try a gap closer to 0.030". It always seemed strange that I was not getting enough cooling effect, yet I thought I was injecting too much alcohol.

This gives me something to try for the weekend.

As I asked Lee above, can anyone describe what it felt like when the spark was "blown out"?

Thanks,
Aaron

 

The blowing the spark out feels like you've got fouled plugs or you're hitting a rev limiter. I ran between .025" and .028" on the Buick.

With the boost and amount of alcohol you're running I'd be tightening the gaps up.

 

good thread guys. I always felt like my car was missing something up top despite 10 psi of boost. The datamaster logs also was showing a drop off past 4500 rpm(despite having a vortech and good breathing heads and hotcam). Maybe a tighter gap is needed. I was currently right around .35, or maybe just slightly less. I think that I need to check them this weekend.

 

Yes, it was exactly like hitting the rev limiter. For the longest time I thought my rev limiter was messed up. I spent alot of time troubleshooting the wrong thing because I would have bet thats what it was.

Lee

 

The last couple of feedback were exactly what I had hoped. My car feels like you are bouncing off the rev limiter. My chip in the MSD6AL has a 6800 RPM chip and I have a new rev-limiter at ~5400.

Cool weather, new plugs, plenty of alcohol, equals new levels of boost.

Thanks to all who replied. This is what I really like about this forum: lot's of varied experiences.

Aaron

 

now that I'm thinking of it, i was getting some phantom detonation at the top of 1st and 2nd gears at the track last time. i didn't see anything popping up on datamaster either. Maybe this was it; it felt like the car was missing.

 

already answered but to reinforce.. yes.. mine at 20psi was all but shutting down on the TR7's gapped at .034".... tightened them to .028"... voila smooth top end.. pinch a little tighter and let us know how she does!

Chris

 

interesting comments guys...

I'm recently experiencing similar things as well running NGK tr7 I'm at .035's as well

Above 6000 i'm feeling similar result right before the rev limiter hits at about 10 pounds of boost. Thinking similar of what AKS was commenting.

I'll have to give it a try also.

Mo

 

So, to those who said they were going to try this...did it resolve your problems?

I have a friend with a SC 5.0 having similar issues, I want to know if I should pass this on or not.

 

I replaced the plugs and gapped to 0.031" and have had non of the "rev-limiter" issues since. My new issue is that I am back to the 2 bar MAP (waiting on a new one that I ordered this week) and it pegs the MAP at ~4900 RPM in this cooler weather.

This thing makes wicked boost.

Aaron

 

This is interesting. I have a 1993 GMC Typhoon, and it does this same thing. I thought it was because I added some fuel and took away spark at anything over 225 kpa, in an attempt to protect my engine from overboost. The Ty's stock wastegate is marginal at best, so I was adding a safety net. After reading the testimonials I am gonna change that gap and see what happens.

 

[QUOTE=USAsOnlyWay]So, to those who said they were going to try this...did it resolve your problems?

I'm going to do this tomorrow...

Mo