Timing VS Compression Buick V6 Tuners come in..

[87chrisss]

Reading thru some older threads i read lots of different compression ratio's and different timing curves but not all on same fuels i see what's safe on these engines on timing advance for pump gas and pump gas w/ alky but how about ethanol? ive seen someone on this forum say they have ran almost 30* + on ethanol is this true? no clue on compression ratio on that comment it was on the e85 thread.. also need some compression 101... what helps get the power on ETHANOL (alcohol based fuels) how high can you go on alcohol based fuels.. can i run higher compression with less timing would this be more beneficial to make power? or is running standard compression somewhere between 8:1-9:5;1 at what point is too much timing hurting performance who runs high compression on this forum? anyone run above 10 to 1 compression with good fuel? im having trouble understanding the timing vs compression thing.. why not run higher compression with less timing make the power with less boost... lastly has anyone ever tried a hemispherical design head on a buick engine? im not an expert if i sound like an idiot to the 25+ year engine builders i apologize but i have to learn somewhere and i dont want my pockets to learn the hard way..thanks,

 

[bison]

It depends on the cylinder fill. The higher the mass efficiency the lower the timing. You need to think about the ex stroke when considering compression ratio based on the backpressure. 9-10:1 is not uncommon.

 

[turbofabricator]

Good that you are asking questions. No such thing as a "dumb" question. Lots of dumb answers, though. One thing to consider is thermal efficiency. As compression increases, so does heat. If you measure combustion temps of two different engines, one being high compression/low boost, the other being low compression/high boost (to equal the same cylinder pressure at 27* after top dead center) the low compression/high boost will have lower combustion temps (especially if you employ an intercooler). High compression turbo charged engines require a very efficient combustion chamber design. Running aggressive timing curves are indictive of a poor combustion chamber design. The goal is to adjust timing so that peak cylinder pressure is reached at approz 27* after top dead center. Ignition lead is needed to get the lfame front to burn and increase pressure in "time". It takes a certain amount of time for the fuel to burn. Advance the timing too much and now it'll detonate, meaning it burns erratically causing huge pressure spikes and subsuquent catastophic engine damage. Each type of fuel has different burn rates.
Spend hours and hours reading engine theory on the 'net and in the library. Speedtalk.com is a great place to read. Google can steer you to other articles pertaining to engine theory. You can spend a life time learning how engines work. I've been building race engines since I was 14 years old. (three weeks ago) So, for the last 36+ years I have been a student of the business and the more I learn and understand, the dumber I feel. Hope this helps.

 

[SloGN]

The best way to find that out on a specific engine and fuel. is to start out a moderate timing say 18 degrees. Slowly advance the timing up and see if the performance or HP increases. ( track/dyno). A EGT meter is a very good way to see what effect the timing is having on combustion temps. But when you are making these changes the A/F ratio should be the same Again at a moderate setting 11:0 is a great place to start. If advanceing the timing up 2-3 degrees don't help the performance then set it back to the lower setting. As higher timing gets you to the knock zone. Then you may try adjusting the fueling to see if the performance picks ups.


Also there is one thing most people don't understand is how the mechanical timing is related to the electrical timning ( Crank sensor) This is really crictical on after market ECU's. But i also i have tested crank sensors that would not trigger until 4-5 degrees later than it should have. so these things can have a dramtic effect on the actual timing the motor is seeing VS what the ECU is calling for.


HTH.


I'm not very intelligent on this stuff. This is what has worked for me and what i have seen over the yrs.

 

[JayC]

I think the BWR engine that came from Anderson was 11:1 and we ran it on straight methanol. Car made a little over 1300 at the wheels on our chasis dyno. As far as timing, I may have the calibration around somewhere and can look. You dont want to go too low with alcohol.

 

[87chrisss]

Thanks, Fabricator i was trying to figure out if Ethanol would help in keeping the engine cooler on a higher compression engine...which is why i was thinking of running a bit higher compression..i know it will increase cylinder pressure and add anything from 15-30 hp just with rasing the CR with just a swap of Headgasket or mill of the head maybe more?... haven't seen much action this thread but i think im going to run some higher compression with e85 and test it out. i really dont want to ruin my motor or my pockets but no one really is posting with do's or dont's what measurement's could i make with ethanol to analyze the limit of my timing curve and or compression ratio?...im assuming an EGT will do it? but i feel like its more complicated than that....i feel i can make some fairly easy hidden HP on just some little tweaks i have brewing in my head..but i dont have the "experience to know if i should keep going... every person i have brought it up to tell me the same thing...high CR and boost dont mix.. even if i have to use a bit of water/alky injection to cool the charge a bit more, with the higher compression and i guess raise timing till i see the limit of what it allows me to do... i'll run some ported heads and unshroud the valves see what i can do with some higher compression.. someone here has to have ran high compression on the street.. im referring to 11+ compression e85 octane is somewhere near 113 from what i have researched on wikipedia...

 

[Alky V6]

I'm running methanol alcohol. I've run 10.45:1, then 11.25:1, and now I'm at 9.25:1.
I've learned that running high compression with boost gives you less leeway with the tuneup. Less room for error. It will also put a hard limit on how much boost you will be able to run. The lower compression levels gives the opposite conditions.
The off boost performance difference between the higher compression ratio and the lower is not significant in my book. I don't feel like I'm missing out on much using the lower compression ratio. On boost performance is identical. The difference is you can run much more boost.
I figured out bmep limits for 11.45 versus 9.25:1. The limit of boost I could run at 11.45:1 was around 22 psi with the fueling I was using. With the same level of fueling and with the 9.25:1 CR, the same bmep limit won't be reached until 40-45 psi boost. Much more room for performance increases and a much wider window for tuning error.

 

[Alky V6]

There is an aftermarket block and heads Volks based H 4 cyl engine that runs methanol and uses nitrous to spool a large turbo, that runs his CR in the 6s to one. He also runs mega boost numbers. He is very, very fast. A record setter.

 

[Alky V6]

As far as timing goes. You will run more with the alcohol due to the slower burn rate of the alcohol fuel compared to gasoline. At 30 psi boost, I've run as much as 36 degrees of timing, and as little as 28 degrees. Not really a whole bunch of difference in performance between the two.
You will definitely notice a drop in power if the timing is too retarded. Boost may ramp up quicker, but rpm ramp up will lag. As you increase timing, you will notice rpm ramp up increase, but at a point, boost ramp up will begin to suffer. I shoot for a timing setting that gives a happy medium between the two. Especially in the operating envelope where the nitrous is involved. You want the boost to rise as quickly as possible, but it's the crankshaft revolutions/minute through the drivetrain that moves the car.

 

[Alky V6]

I have found that when you get close to that sweet spot with the timing, just a 1/3 degree change will make a noticeable difference in the rpm acceleration ramp up curve. If there is a section in the rpm rise rate where the rpm rise rate slouches a little, I can make a 1/3 of a degree change in the timing table cell that affects that section of the rpm ramp up curve and see a noticeable change in that section of the curve. Goes to show you that when you think you're getting close to detonation limits, you don't want to be making 3 degree changes. More like 1/2 a degree.
This also shows the advantage of having a very accurate ignition timing system. If you have a system that scatters the timing an appreciable amount, you can see how dangerous it can be to run the ignition timing too close to detonation limits.

 

[canadian nascar]

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[we4Mateo]

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[bison]

Also there is one thing most people don't understand is how the mechanical timing is related to the electrical timning ( Crank sensor) This is really crictical on after market ECU's. But i also i have tested crank sensors that would not trigger until 4-5 degrees later than it should have. so these things can have a dramtic effect on the actual timing the motor is seeing VS what the ECU is calling for.

Anyone building or tuning a high hp engine should have these types of things straightened out. Ive seen a bigger issue with various dampers and hubs. The timing indicated accuracy is only as good as the persons ability to verify that it is what it should be. Offsetting timing is one of the first steps after firing a new engine. Another reason a dyno is so valuable.

 

[SloGN]

Anyone building or tuning a high hp engine should have these types of things straightened out. Ive seen a bigger issue with various dampers and hubs. The timing indicated accuracy is only as good as the persons ability to verify that it is what it should be. Offsetting timing is one of the first steps after firing a new engine. Another reason a dyno is so valuable.

You would be surprised at how many people out there don't understand this. Whats even more of a problem is the stock ECU guys that can't trim the crank angle ref. So one must remember the offset difference when adding in timing using external devices.




Not to Hijack the thread here.

do you know how much spark scatter the c3I systems have?

 

[bison]

You would be surprised at how many people out there don't understand this. Whats even more of a problem is the stock ECU guys that can't trim the crank angle ref. So one must remember the offset difference when adding in timing using external devices.



Not to Hijack the thread here.

do you know how much spark scatter the c3I systems have?

The offset can be burned into the chip.