Leaving power on the table...HPvs BOOSTvsCOMPRESIONvsTIMING

[fastblackracing]

I recently got my car up and running and spent a few hours at the dyno getting some driveability issues sorted out and some power pulls worked on. We ran out of time and will get back on it next spring. We ended up at 680 hp at 30# with 19 degrees timing on a mustang dyno. The compression on this engine is 8.2 to 1. I feel that there is probly another 40 HP or so left in this combo when we get back to it. My question is what would raising the compression another 1 to 1.5 points be worth power wise? Once the combo is maxed out, how much would you lower the boost and raise the compression to be power ahead? 3# less boost 1 point more compression = more power? Does any one have an idea? Is the answer to this related to back pressure in the turbo, what should I be looking for on the back pressure, a certain number, a ratio to boost pressure, a sharp rise in the backpressure curve? How much would timing change with more compression? Right now the power peaks at 6200 and is pretty flat from 6000-6500. Little engine 233 inch needs more power pulses higher rpm, I may have to change my rear gear to make it work. Sorry this is kinda long whinded but I am able to start gathering stuff for my next engine right now and am and looking to be more purpose built. The next one will be in 260 to 278 inch range. Fuel is c-16 and I will be staying with a 3 bolt housing most likely. Just thinking outside the box and trying to learn. Thanks, Mannie

 

[turbobitt]

What fuel ? Why reduce boost when going up in compression ? I think you have a little more room with timing if your running 116 octane.
AG.

 

[fastblackracing]

C16 now, how much room do you think? Im thinking If compression goes up you will not be able to max out at the same boost level before getting into detonation.

 

[earlbrown]

That's an oversimplistic question. There's way to many factors to consider.

 

[turbobitt]

C16 now, how much room do you think? Im thinking If compression goes up you will not be able to max out at the same boost level before getting into detonation.

Well. without getting into specifics I'm running 9:1 and way more timing than 19 degrees at 30# boost. I plan on pushing boost a lot higher and obviously pulling timing at the same time. You just need to nail down all the specifics when tuning the car. The very first thing is making sure your balancer is reading correctly and check the base timing with a light and make appropriate corrections.
AG.

 

[SS/GN]

Interesting thought. In regards to compression , how much does quench effect these motors. On N/A engines its huge. I have often thought about the dish piston vs a flat top and the quench area involved.

 

[fastblackracing]

Well. without getting into specifics I'm running 9:1 and way more timing than 19 degrees at 30# boost. I plan on pushing boost a lot higher and obviously pulling timing at the same time. You just need to nail down all the specifics when tuning the car. The very first thing is making sure your balancer is reading correctly and check the base timing with a light and make appropriate corrections.
AG.

The balancer was measured and marked during the build, Timing has been verified. You are running stage 2 heads? Mine are champion gn1. dont know how this plays into it?

 

[fastblackracing]

Interesting thought. In regards to compression , how much does quench effect these motors. On N/A engines its huge. I have often thought about the dish piston vs a flat top and the quench area involved.

This is something I have wondered about also, have not found much buick v6 related on this if it would benefit to design a piston to mirror the head with a quench pad? May not be able to get enough dish -cc to maintain a sensible compression ratio? Seems some of the higher HP nitrous guys v8 are running very large quench clearances. Whatever thats worth.

 

[Mr.Spool]

We ended up at 680 hp at 30# with 19 degrees timing on a mustang dyno

how aggressive do you want to get with the car?i have run both high and low comp motors and will say you can run big boost on the higher comp with the right combo and tune.the thought of going up in comp and lowering boost to make power is counterproductive as boost is just a number.the better the airpump you have will change the boost number but the turbo really has to be capable of moving the air.

 

[Jerryl]

I am no expert but wondering if you ever measured exh pressure.

 

[fastblackracing]

how aggressive do you want to get with the car?i have run both high and low comp motors and will say you can run big boost on the higher comp with the right combo and tune.the thought of going up in comp and lowering boost to make power is counterproductive as boost is just a number.the better the airpump you have will change the boost number but the turbo really has to be capable of moving the air.

How aggressive? I usually end up pretty much maxed out on the turbo. Are you saying that if my 8.2 -1 engine maxes out at 40# of boost right at the point of detonation I would be able to raise the compression to 9.5-1 and still run 40# of boost safely? My current combo is making 36# out on the street with very little effort. I am talking about maxing out my current combo [8.2-1] and if you raised it to 9.5-1 where would it max out. Still 40#?

 

[fastblackracing]

I am no expert but wondering if you ever measured exh pressure.

I am no expert but wondering if you ever measured exh pressure.

Jerryl, I will be logging back pressure when the car comes back out next spring. I feel this is part of the question I am asking.

 

[turbobitt]

How aggressive? I usually end up pretty much maxed out on the turbo. Are you saying that if my 8.2 -1 engine maxes out at 40# of boost right at the point of detonation I would be able to raise the compression to 9.5-1 and still run 40# of boost safely? My current combo is making 36# out on the street with very little effort. I am talking about maxing out my current combo [8.2-1] and if you raised it to 9.5-1 where would it max out. Still 40#?

I'm not sure I understand or agree with your statement of maxed out at 40# at the point of detonation. What gives you this impression ?
AG.

 

[fastblackracing]

I'm not sure I understand or agree with your statement of maxed out at 40# at the point of detonation. What gives you this impression ?
AG.

What I am trying to say is with my current combo [8.2-1] there will eventually be a limit to how much boost the motor wants before it goes into detonation. Lets just say Its 40#. And lets just say the motor makes 740 HP at that point. Now lets say The same motor had 9.5-1 compression, rest of the combo stays the same. Will it still take 40# of boost before it hits the detonation threshold? I dont think it will, it will probly be less. How much less is the question and lets say its 5# less. Will it it make more power with 35# and 9.5-1 or 40# and 8.2-1 ? Does this make any sense? And yes the turbo is capable of moving enough air to do this.

 

[turbobitt]

I don't really think your going to hit any detonation threshold with C-16 at your current timing. If the timing is to advance I'm sure it can lift a head but that isn't going to limit boost. Bison and I have this conversation all the time. Its all about leaving your comfort zone and trying something different. If the turbo can move more air at 40 psi than should pull some timing and go there.
AG.

 

[Mr.Spool]

What I am trying to say is with my current combo [8.2-1] there will eventually be a limit to how much boost the motor wants before it goes into detonation. Lets just say Its 40#

No you could experience hard parts failure before detonation.

 

[Mr.Spool]

How aggressive? I usually end up pretty much maxed out on the turbo. Are you saying that if my 8.2 -1 engine maxes out at 40# of boost right at the point of detonation I would be able to raise the compression to 9.5-1 and still run 40# of boost safely?

The turbo may not make 40 psi with the raised compression.

 

[bison]

The turbo may not make 40 psi with the raised compression.

This is correct


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[fastblackracing]

The turbo may not make 40 psi with the raised compression.

This is correct


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Why is this bison? What changes in overall dynamics that limit the turbo to make boost at higher pressures?

 

[turbobitt]

More exhaust energy adding to back pressure overrunning the turbine.
AG


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