Finished!! Forged piston block, Custom valve head (flowbenched)

[Ondonti]

Quote:

Originally Posted by c2xejk That is not quite right. You can/need to run more advance because the combustion chamber is bigger and it takes longer for the flame front to cover the whole chamber. When you advance the timing you are lighting the mixture off before Top-Dead Center (TDC.) So the initial burning A/F mixture is actually trying to push the crankshaft _backward_. In an ideal world you would want to light the mixture after TDC so none of the fuel is used to push the crankshaft backwards. There is actually an angle where you want to put the peak cylinder pressure (it based on engine geometry...) If you look at some of the gains made by racers it has been by using a more efficient combustion chamber and being able to make peak-hp with _less_ spark advance. One of these days Mike or I need to do a write-up about spark hooks. But the bottom line is as you increase spark advance, hp will go up, peak and then go down. The exact shape and position of the spark hook is dependent on the complete engine configuration. As we were tuning the spark advance on my van we could see this effect with successive dyne pulls. We advanced the timing (small changes) until peak hp went down, then went half way in between and found the peak. Advancing the timing any further would have only hurt hp.

Im not sure what the point of your post is as "theoretical" does little for a reality it cant be applied to.

I know what ignition advance is and the limitations of it. I dont need information that is totally irrelevant. Why are you being a jackass pretending I dont know what ignition advance is?

And the fact of racing is when you are not modifying the efficiency of the chamber, 99% of the time you will run as much advance as possible without the motor detonating, and often more timing is better then more boost.

This post belongs someplace else.

I dont really care about "what would be perfect" because perfect would be a 100% methanol engine running 15:1 compression with 4 valve heads and tons of boost. I am not building a high compression methanol 4 of 5 valve engine.

It is well known among tuners that ignition advance can make up for most of what is lost with lower compression and lower compression will make more power on the same octane.

And I will never run c16 or any other race gas in the motor so advice based on factors which have nothing to do with me are pointless.
Not to mention there isnt an internal combustion engine that could get away with no advance.
I dont understand your bad attitude here when its all based on a "perfect" motor which doesnt exist (and I certainly dont own).

Low compression motors need more advance. I know you cant refute that and you are just blabbering. Talking about how to avoid using more ignition advance by building a different motor has NOTHING to do with this.

Most of all, I was never talking to you until you pretended to be confused, and now you are blabbering something which has nothing to do with my car

[c2xejk]

I am sorry I stepped on your toes. That was not my intent. My intent is and has been to understand better what and why things work (or don't.)

I am more curious if you are seeing hp gains from advancing the timing that far.

I will save talk about theoretics to other forums...

[Ondonti]

Obviously its about 99.9% impossible to tell without dyno testing unless the car was very very consistent at the race track. And i doubt the car will be consistent anytime soon.

But running 8-10 degrees more timing then stock after lowering compression 2 full points is not very aggressive. Like I said though, I didnt even check the timing on that car. I probably will just so I can know what it is set to right now for future reference.

[comp]

Quote:

Originally Posted by Ondonti Obviously its about 99.9% impossible to tell without dyno testing unless the car was very very consistent at the race track. And i doubt the car will be consistent anytime soon. But running 8-10 degrees more timing then stock after lowering compression 2 full points is not very aggressive. Like I said though, I didnt even check the timing on that car. I probably will just so I can know what it is set to right now for future reference.

what is the total timing and with how much max boost ???

[c2xejk]

Quote:

Originally Posted by Ondonti Obviously its about 99.9% impossible to tell without dyno testing unless the car was very very consistent at the race track. And i doubt the car will be consistent anytime soon. But running 8-10 degrees more timing then stock after lowering compression 2 full points is not very aggressive. Like I said though, I didnt even check the timing on that car. I probably will just so I can know what it is set to right now for future reference.

Understood. I agree that running 8-10 degrees more is not a problem given your setup. I wasn't sure if you were seeing/feeling something that encouraged you there or if that is the baseline for continued tuning...

You are getting some impressive results.

[87turbodance]

Quote:

Originally Posted by c2xejk If you look at some of the gains made by racers it has been by using a more efficient combustion chamber and being able to make peak-hp with _less_ spark advance.

My understanding is that this is one of the advantages of the more modern pent roof combustion chamber? Smaller, tighter and faster burning combustion chamber allowing more power with less timing and an overall more efficient combustion. This is why I have been looking at mounting the 24V heads to our 3.0 12V block. I believe overall efficiency will improve and allow more boost and timing to be run at a higher compression ratio for better off boost efficiency and performance.

[Shadow24V]

and you want to run LESS timing with the 24v heads?

whats the max timing on the 12v motor (modified or normal) 12-20* at most? the Hi-Po spark map i have off of a known good boosted 24v (i only got the N/A part) runs up to 32.5* advance on a 9:1 CR motor

somethings not adding up in my head there lol

[c2xejk]

I have started a new thread to discuss the spark advance and 2 vs 4 valve conversation. (2 vs 4 valve/cyl heads, their capabilities and the impact on tuning )

[Ondonti]

Quote:

Originally Posted by c2xejk Understood. I agree that running 8-10 degrees more is not a problem given your setup. I wasn't sure if you were seeing/feeling something that encouraged you there or if that is the baseline for continued tuning... You are getting some impressive results.

I havent messed with the timing for a few years. I believe I just set it where the engine seemed to idle more aggressively at the time.

[Ondonti]

Quote:

Originally Posted by Shadow24V and you want to run LESS timing with the 24v heads? whats the max timing on the 12v motor (modified or normal) 12-20* at most? the Hi-Po spark map i have off of a known good boosted 24v (i only got the N/A part) runs up to 32.5* advance on a 9:1 CR motor somethings not adding up in my head there lol

12-20 degrees is just the base timing. Then there is the ignition advance calculated into the computer.

Looking at an 89 calibration in Dcal.

+1.5 degrees advance when the MAP is WOT (near zero, 14 degrees near full vacuum)

+5 degrees from warm engien + WOT
-6 degrees engine warm

-42 degrees 5000 rpms simulated mechanicl advance
+47.5 degrees 5000 rpms Max advance
-------------
so +6 degrees to the base timing.............Which is really low.

But I dont really understand the mechanical advance table because it gives negative numbers. I really think it is a positive number though and then the MAX advance table prevents it from going any higher then 47.5 degrees.

59.5 (12 degrees base) degrees seems like WAY to much ignition advance.

[Ondonti]

I made these to hold up the rear hatch better. It was sagging and banging around because it wasnt well supported.

Showing off my new light after the oldschool had a little fire inside.
Note the tires which belong to Bansheenut.

[Ondonti]

Well the really old slicks I have dont seem to hook up.
It was too windy today to run the full 1/4.
My 1/8th was horrible. I ran two 9.0@81-82 1/8th mile.
Then I found out that my drivers side slick was touching the strut, so that is why my car was pulling HARD to the left. I redid the camber on that side so it wasnt really touching anymore, and then ran even slower (9.39@81) because the slicks just wouldnt grab. It was also my worse 60' of 2.172. My 9.0 runs had a 2.07 I think and then a 1.97.
Whats bad is that shifting into second, the car still wont hook properly.

We have videos of it running the 1/8th. I will get around to posting something.

What has me pissed is that the turbo spirit ran the same 82mph 1/8th trap as this car on kumho seasonal street tires, and almost the same 1/8th E.T.

The spirit was really really easy to drive, this car is not...and I do not have my shift points down as I cant really watch the tach much and I havent driven the car enough to know the sound of the engine when its time to shift. Its hard with the turbo and open wastegate because it all starts sounding the same in the higher rpms.

I was comparing my slicks to Bansheenuts slicks this evening and I am thinking that mine might be really really old (they are at least 4-5 years old and could be twice that age). And they have not been treated well by the 3+ previous owners :P

[Shadow24V]

each car is different. get some new slicks and a shift light maybe? ill probably suck bad on weds too: ok tune and noob driver

do they have boost limiters? a way to keep first at say 5psi, 2nd at 8 and 3rd+ at full boost?

[kreel]

If the slicks really are that old they could be delaminating (sp?) and falling apart. +1 on getting new ones.

[lookin]

Brent your engine compartment is amazing!

side note: It now takes forever to open any page here, pics or not, because of all the td.c banners, tags and adds! The server code is just plain bad, and it connects to everything from google to tribal-fusion. What a mess. I am drowned in excessive content even after the pages finally do download. Time for me to read a different forum I guess.