Quench Question

[stealth]

I may have missed it, what's the final cp ratio calculate to and what fuel?

[perfconn]

14.30 using Renegade 112 or Late Model Plus

[Bigchief632]

The only negative, is that it will want more total timing to make it's best power and will probably want a bit more fuel also, so the bsfc's will be higher than usual, and It will make a bit less TQ than usual for an sb2 combo. It won't detonate.

[RDY4WAR]

I say ditch the Renegade and run VP C25.

[mt-engines]

I say ditch the Renegade and run VP C25.

WTF? he's not 18:1 compression.

Ditch the $10/gal fuel for $27/gal fuel?

[RDY4WAR]

I say ditch the Renegade and run VP C25.

WTF? he's not 18:1 compression.

Ditch the $10/gal fuel for $27/gal fuel?

It's not about the compression. VP C25 is a mid-high rpm NA engine's dream fuel. It vaporizes easily, burns quickly, and makes power. Renegade 112 is no such fuel with too high of a distillation curve and too low of a RVP.

VP C25 was.the fuel used in NHRA Pro Stock up until the switch to EFI. Sunoco then got a dirty contract with NHRA to force SR18 in Pro Stock which is largely responsible for the major hit in power the teams got with that transition.

[Schurkey]

I've run .130 without signs off detonation

Sure. Because with that much clearance, the chamber is "open".

The big problem is when the clearance is more than ideal, but less than "open" chambered. Too much gap to provide mixture motion, or to push end-gasses out of the quench area, but not enough clearance to allow the flame travel inside the quench area. So there's lots of end-gasses being squeezed and heated until they spontaneously combust (detonate.)

Add some more clearance, you may have slow combustion requiring more spark advance--but the flame front goes all the way across the piston so the end-gasses burn instead of detonate.

I've heard the "danger zone" is anywhere between .050 and about .100 or so. But I'm sure that varies with the area of the quench pad(s) on the head, RPM, air/fuel ratio, etc.

[Tom68]

Engine is already together just waiting on intake spacers.I asked the question because I was wondering how the engine will act on dyno if detonating.Pictures of 33.4cc chambers & 4.135 bore pistons.

Well the HC emissions should be low, although the top ring appears to be a long way down.

I predict good results from this big quench clearance.

[perfconn]

Thanks all.Should have it on dyno next week if intake spacers come in.Last all aluminum 431ci SB2.2 made 850hp @ 7000rpm & 681# torque @ 6200 rpm.This is first 4.125 stroke I have done.Not built exactly how I would prefer but we will see what it does.Any suggestions on timing to try.The 4" strokes like 28*

[Bigchief632]

Thanks all.Should have it on dyno next week if intake spacers come in.Last all aluminum 431ci SB2.2 made 850hp @ 7000rpm & 681# torque @ 6200 rpm.This is first 4.125 stroke I have done.Not built exactly how I would prefer but we will see what it does.Any suggestions on timing to try.The 4" strokes like 28*

Yeah they usually like 28-30 from what I've seen, sb2 stuff, and are very sensitive to timing. I've seen them lose .3 and 5mph at the drag strip when the timing was accidently set at 38 when it wanted 30. Couldn't figure it out. Once we discovered the problem, et/mph back on next pass. That's probably 50+hp. So, my prediction it will want 34ish.

[Bigchief632]

I say ditch the Renegade and run VP C25.

WTF? he's not 18:1 compression.

Ditch the $10/gal fuel for $27/gal fuel?

It's not about the compression. VP C25 is a mid-high rpm NA engine's dream fuel. It vaporizes easily, burns quickly, and makes power. Renegade 112 is no such fuel with too high of a distillation curve and too low of a RVP.

VP C25 was.the fuel used in NHRA Pro Stock up until the switch to EFI. Sunoco then got a dirty contract with NHRA to force SR18 in Pro Stock which is largely responsible for the major hit in power the teams got with that transition.

C25 is good stuff

[Dave B]

Thanks all.Should have it on dyno next week if intake spacers come in.Last all aluminum 431ci SB2.2 made 850hp @ 7000rpm & 681# torque @ 6200 rpm.This is first 4.125 stroke I have done.Not built exactly how I would prefer but we will see what it does.Any suggestions on timing to try.The 4" strokes like 28*

I have never seen a sb2 done at 7000,did you cam it that way short? All of our 400-440 dirt engines or drag make power 7800 plus.I would be damn depressed if not 960 hp plus with those components and that cubic inch.Quench is waaayyyy over rated like cranking compression numbers!! If a guy can't afford great fuel like c25 in a quality race engine they should just hang it up. We ran it in 11.5 to 1 comp 280-300 inch stuff for ever.

[Dave B]

Thanks all.Should have it on dyno next week if intake spacers come in.Last all aluminum 431ci SB2.2 made 850hp @ 7000rpm & 681# torque @ 6200 rpm.This is first 4.125 stroke I have done.Not built exactly how I would prefer but we will see what it does.Any suggestions on timing to try.The 4" strokes like 28*

Why would you kill compression in the engine? We just finished my oldest brothers sb2 platform deal. We softened chamber just a little for e85 fuel.Its still 16.88 to 1 comp. We have ran several in 17s and right at 18.
I guess we are doing this wrong ? I guess we spend allot on a engine platform and expect it to perform. We will be getting a new sheet metal intake and top mated together today or tomorrow for it. My thoughts on this one is near 9000 rpm running area and 1100 hp. Not once did quench value ever even considered or cared about in this build.Its like Nike, just do it.

[perfconn]

I understand most of you dudes give drag race recommendations but this engine was built for the dirt late model market.You don't run any dirt engine at 9000rpm.I build the engines to last 1000 - 1200 laps or customers won't come back.I looked & I don't have a dyno sheet on last 431-sb2.2 but I do have one of 438ci that I put in a Dart Iron Eagle block with a 4" stroke,55mm cam,.937 lifters.Made 867hp @ 7500rpm.

[perfconn]

By the way Tom B,one way is not right & the other way wrong,just different.