Baffled

[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.

[GregWeld]

Originally Posted by Track Junky

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.

Oh I don't really use 9 gallons per session buddy - just pulling your leg.... But it is 9 gallons per fill up ---- and that's about 2 sessions... so 4.5 to 5 gallons per is similar to what you're seeing.

[GregWeld]

Gaetano ---- Regardless of all the gas and timing discussion ---- you need to FIND the right timing for YOUR motor. That could be 32* or it could be 36* and anywhere in-between.


I don't think you can find that with just seat of the pants driving. And damage can occur if you get it wrong - so it's more than just a little important.

[Vince@Meanstreets]

dyno time is the only imho. Your engine numbers and AFR's will tell you what it wants.

[Track Junky]

Originally Posted by GregWeld

Gaetano ---- Regardless of all the gas and timing discussion ---- you need to FIND the right timing for YOUR motor. That could be 32* or it could be 36* and anywhere in-between.


I don't think you can find that with just seat of the pants driving. And damage can occur if you get it wrong - so it's more than just a little important.

Yeah I get it. Joe said the same thing when he was dyno tuning my motor. 32.5* total is what he came up with. Don't know or remember exactly how he came to that conclusion but we made over 20 pulls and a few changes and he would pull spark plugs and inspect them with some sort of spark plug magnifying scope gismo.
I'm trying to schedule Joe for a chassis dyno tune at Sonoma the Friday before the event since I put another distributor in and the springs on the original distributor don't look the same as the ones I'm using now.

[Vince@Meanstreets]

Originally Posted by Track Junky

Yeah I get it. Joe said the same thing when he was dyno tuning my motor. 32.5* total is what he came up with. Don't know or remember exactly how he came to that conclusion but we made over 20 pulls and a few changes and he would pull spark plugs and inspect them with some sort of spark plug magnifying scope gismo.
I'm trying to schedule Joe for a chassis dyno tune at Sonoma the Friday before the event since I put another distributor in and the springs on the original distributor don't look the same as the ones I'm using now.

Don't forget we can schedule a chassis dyno session with Joe over at Borelli's. They can set up fo AFR's and it may save down time. Aaron say saturdays would be good.

[GregWeld]

Originally Posted by Track Junky

Yeah I get it. Joe said the same thing when he was dyno tuning my motor. 32.5* total is what he came up with. Don't know or remember exactly how he came to that conclusion but we made over 20 pulls and a few changes and he would pull spark plugs and inspect them with some sort of spark plug magnifying scope gismo.
I'm trying to schedule Joe for a chassis dyno tune at Sonoma the Friday before the event since I put another distributor in and the springs on the original distributor don't look the same as the ones I'm using now.

GOOD 'cause it's way cheaper than new motors.