Baffled

[Flash68]

Originally Posted by Track Junky

My car is going to use gas like a Prius compared to yours. I filled my tank at Sonoma and then ran a full session. Went back to the pumps and refilled just to get an idea of how much fuel I used........only 4.3 gallons

Sounds like a part throttle session to me. Step on it would ya?

[Track Junky]

Originally Posted by Flash68

Sounds like a part throttle session to me. Step on it would ya?

That's fricken funny......and you could be right

[Shmoov69]

Originally Posted by Flash68

Sounds like a part throttle session to me. Step on it would ya?

Sheesh! That's what I was thinking!! 4.3 gallons on a track day?!? The only time didn't use more (like 2-3 times that!) was wen it was broke on the trailer after a few runs! LoL!

[intocarss]

Originally Posted by Flash68

I disagree with Greg to a point on timing needed. Compression is part of it but the efficiency of the heads/combustion chamber has a big part to do with it.

Based on your theory Greg, tell me why my motor likes 30* timing (13:1 compression) and Rob's FE likes near 40* (less than mine, around 12:1 give or take).

It's mostly due to the difference in combustion chamber, valve angle, etc.

Typical 23* headed engines do not run low timing (relatively) like 32* so that is very surprising. 36-38* sounds more like it. I am thinking Joe built in a lot of safety for you? I dunno else why. That doesn't make much sense to me based on what you've shared.

[Track Junky]

Originally Posted by Shmoov69

Sheesh! That's what I was thinking!! 4.3 gallons on a track day?!? The only time didn't use more (like 2-3 times that!) was wen it was broke on the trailer after a few runs! LoL!

You do realize I'm just talking about one session out of the 4 total for the day right Jimmy

[GregWeld]

Originally Posted by Track Junky

That's some interesting info Greg. I didn't know higher compression likes more timing. When I originally dynode this motor in Muncie, Indiana at the builder shop we went with 38* total timing.

When I dyno tuned down here after the timing chain incident Joe thought it ran best at 32.5*.

Well a dyno is the PROPER way to build a real tune on any motor....

I'd be running 36* in that motor to start with and see if it likes it.

Originally Posted by Flash68

I disagree with Greg to a point on timing needed. Compression is part of it but the efficiency of the heads/combustion chamber has a big part to do with it.

Based on your theory Greg, tell me why my motor likes 30* timing (13:1 compression) and Rob's FE likes near 40* (less than mine, around 12:1 give or take).

It's mostly due to the difference in combustion chamber, valve angle, etc.

Typical 23* headed engines do not run low timing (relatively) like 32* so that is very surprising. 36-38* sounds more like it. I am thinking Joe built in a lot of safety for you? I dunno else why. That doesn't make much sense to me based on what you've shared.

It has EVERYTHING to do with combustion efficiency.... and heads and the propagation of the flame travel etc. However..... High compression only tells you what gas you're going to have to run -- it doesn't tell you what timing a motor is going to need / want.

The fuel - in this case - is what leads me to the timing in question. So assuming he has good heads - aluminum - we know he has high compression -- and the numbers he's tossing out is the STATIC compression number of the piston --- because what really counts is the CYLINDER PRESSURE -- and that depends on his cam numbers. But 114 octane gas is going to want more timing than pump fuel.

Originally Posted by Track Junky

Nope. Build sheet shows 14:1. Piston part number shows 15:1

Really doesn't matter except the high compression is going to want high octane fuel in order to stave off detonation. Thus the only real reason to understand that part of the motor.

Originally Posted by Track Junky

You do realize I'm just talking about one session out of the 4 total for the day right Jimmy

I burn about 9 gallons per session.... might have something to do with how often a guy is WOT..... LOL

[GregWeld]

BTW -- For the record --- WE ARE ALL JUST GUESSING....


Mines just a more educated guess.

[Track Junky]

Originally Posted by GregWeld

I burn about 9 gallons per session.... might have something to do with how often a guy is WOT..... LOL

We've chatted about this before. That is weird. Not sure why your using so much fuel.........Same deal at T-Hill. I use about 5 gallons a session there and our lap times as of late have been pretty close.

[Shmoov69]

Originally Posted by Track Junky

You do realize I'm just talking about one session out of the 4 total for the day right Jimmy

No, actually I didn't realize that. Not sure how big the track is there and how many laps, so I can't comment on what mine "would be" there. All I know is that I had to fill like 3 times at Putnam park when I ran there a couple different times. And that was going in with a full tank.

But glad that you may be figuring it out that it could be the gas. It sounded to me like an ignition issue, but if for some reason fuel isn't burning, then it would seem like ignition. I'm anxious to see what you find to be the real issue. Lots of discussion and learning going on here

[GregWeld]

Originally Posted by Flash68

I disagree with Greg to a point on timing needed. Compression is part of it but the efficiency of the heads/combustion chamber has a big part to do with it.

Based on your theory Greg, tell me why my motor likes 30* timing (13:1 compression) and Rob's FE likes near 40* (less than mine, around 12:1 give or take).It's mostly due to the difference in combustion chamber, valve angle, etc.

Totally agree with you --- until we toss in the 114 octane.
You can not compare two completely different motors -- all that will tell you is that they are completely different. For many obvious reasons.


A good running MOPAR 440 --- wants 40* total on PUMP gas with good heads. That's NOT a SBC.... or a FORD for that matter. Different motors want different timing.

Originally Posted by Flash68

23* headed engines do not run low timing (relatively) like 32* so that is very surprising. 36-38* sounds more like it. I am thinking Joe built in a lot of safety for you? I dunno else why. That doesn't make much sense to me based on what you've shared.

Good heads -- tight quench -- etc -- my 408 motor ran 34* and made best power. A dyno is going to tell you -- you don't tell it. You find it. The numbers don't lie. It was also running PUMP GAS not 114.