High-Comp Time!
04-08-2010, 04:28 AM
#22
Thanks Guys!
Regarding the compression ratio, the pistons have an 11.5cc dome, which if I am correct will result in around a 12.1:1 compression, not the actual target 12.3. The little bit of material around the spark relief is another 0.3~ cc's.
From my understanding, I should be seeing roughly 5% power for each point of compression (up to a point, of course), so the 2 points could in theory net 30 wheel. I don't expect that and will be happy with anything more than 15.
E85 is a great idea, I don't know much about it. For endurance racing I believe the fuel consumption is higher so that might be a problem for our current 1.5hr stint strategy, the cell just isn't big enough. I'd also have to check the bladder in my cell and make sure that it's ok to use with alcohol.
Regarding the compression ratio, the pistons have an 11.5cc dome, which if I am correct will result in around a 12.1:1 compression, not the actual target 12.3. The little bit of material around the spark relief is another 0.3~ cc's.
From my understanding, I should be seeing roughly 5% power for each point of compression (up to a point, of course), so the 2 points could in theory net 30 wheel. I don't expect that and will be happy with anything more than 15.
E85 is a great idea, I don't know much about it. For endurance racing I believe the fuel consumption is higher so that might be a problem for our current 1.5hr stint strategy, the cell just isn't big enough. I'd also have to check the bladder in my cell and make sure that it's ok to use with alcohol.
05-14-2010, 07:21 AM
#26
Thanks!
Well you guys would be amazed, the higher compression pistons yielded absolutely no gains what-so-ever. Infact, the dyno plot basically was a carbon copy of what it was with the stock engine.
Two tests were performed:
Stock intake manifold, throttle body and Skunk2 spacer
AND
Our aluminum box with open 3.5" hole in the top.
Both plots look identical to the power you've seen before, which was quite amazing. The only changes other than the pistons and rods were Mark II racing fuel and NGK racing spark plugs that have more clearance to the plug.
The engine has now developed a nasty vibration or flex that is causing the flywheel to actually hit, and destroy the crank angle sensor only at very high rpm under very high load!
It's really quite amazing. Other than that the engine runs perfectly, has great oil pressure, doesn't smoke etc.
The flywheel has been off and inspected, we even did some tests to try and figure out exactly when the flywheel is "growing" and it seems to be happening ONLY above ~4500rpm.
I tuned the traction control on the Motec M800 and god damn the car sounds amazing at full load 7000rpm with 50% ignition cut, you just have to hear it. Ahhhh
And then right after that glorious moment, the crank angle sensor is destroyed and she just silently rolls to a stop. It's really sad.
Well you guys would be amazed, the higher compression pistons yielded absolutely no gains what-so-ever. Infact, the dyno plot basically was a carbon copy of what it was with the stock engine.
Two tests were performed:
Stock intake manifold, throttle body and Skunk2 spacer
AND
Our aluminum box with open 3.5" hole in the top.
Both plots look identical to the power you've seen before, which was quite amazing. The only changes other than the pistons and rods were Mark II racing fuel and NGK racing spark plugs that have more clearance to the plug.
The engine has now developed a nasty vibration or flex that is causing the flywheel to actually hit, and destroy the crank angle sensor only at very high rpm under very high load!
It's really quite amazing. Other than that the engine runs perfectly, has great oil pressure, doesn't smoke etc.
The flywheel has been off and inspected, we even did some tests to try and figure out exactly when the flywheel is "growing" and it seems to be happening ONLY above ~4500rpm.
I tuned the traction control on the Motec M800 and god damn the car sounds amazing at full load 7000rpm with 50% ignition cut, you just have to hear it. Ahhhh
And then right after that glorious moment, the crank angle sensor is destroyed and she just silently rolls to a stop. It's really sad.
05-14-2010, 11:43 AM
#31
kacz07: well I got that.... I just thought that with N/A builds compression was part of the HP gain. With other engines adding compression usually boost HP, so the fact that the VQ35DE doesn't respond to raising compression is odd. Does this mean there is something else restricting the engine, that we don't see,because its not taking advantage of the added compression?
this is on stock cams right? I'm guessing cams are the key to unlocking these engines.
*edit*
these pistons 95.5 or overbore to 96mm??
this is on stock cams right? I'm guessing cams are the key to unlocking these engines.
*edit*
these pistons 95.5 or overbore to 96mm??
Last edited by SexyRob; 05-14-2010 at 11:52 AM.
05-14-2010, 12:28 PM
#32
kacz07: well I got that.... I just thought that with N/A builds compression was part of the HP gain. With other engines adding compression usually boost HP, so the fact that the VQ35DE doesn't respond to raising compression is odd. Does this mean there is something else restricting the engine, that we don't see,because its not taking advantage of the added compression?
this is on stock cams right? I'm guessing cams are the key to unlocking these engines.
*edit*
these pistons 95.5 or overbore to 96mm??
this is on stock cams right? I'm guessing cams are the key to unlocking these engines.
*edit*
these pistons 95.5 or overbore to 96mm??
Last edited by kacz07; 05-26-2010 at 04:11 PM.
05-14-2010, 12:51 PM
#33
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I'm sorry if you said this already. What flywheel are you using? Are you sure the balancing was done correctly and well enough? I can't imagine a tune can be any good with machanical problems. I am by no means talking bad about you or the machine shop/builder. I'm just raising the question and getting insight.
07-05-2010, 09:53 PM
#36
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It will be very interesting to see the power increase that these pistons achieve.
In 2003 I had a talk with the boss of Nissan Motorsport South Africa.
They were the builders of the factory Paris-Daker rally raid Pathfinders.
In the conversation he said that the DE made good power up to 12.5 CR with very little to be gained above this. He also said to use the 46cc Nismo heads to increase the CR so as to keep the original combustion chamber & piston design.
Because of the intended use of the motor ( Long distance, high revving & high temp desert racing ) they settled on 11.0 CR but still made over 400 HP @ the flywheel by using Jenvey ITB's, Pectel ECU & some very high lift cams.
In 2003 I had a talk with the boss of Nissan Motorsport South Africa.
They were the builders of the factory Paris-Daker rally raid Pathfinders.
In the conversation he said that the DE made good power up to 12.5 CR with very little to be gained above this. He also said to use the 46cc Nismo heads to increase the CR so as to keep the original combustion chamber & piston design.
Because of the intended use of the motor ( Long distance, high revving & high temp desert racing ) they settled on 11.0 CR but still made over 400 HP @ the flywheel by using Jenvey ITB's, Pectel ECU & some very high lift cams.
were the jenvey dealer in the US here , the same set on Ivory and Kgkeen VQs.
I wouldnt mind seeing more images pop up of the setup
07-05-2010, 09:56 PM
#37
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T
E85 is a great idea, I don't know much about it. For endurance racing I believe the fuel consumption is higher so that might be a problem for our current 1.5hr stint strategy, the cell just isn't big enough. I'd also have to check the bladder in my cell and make sure that it's ok to use with alcohol.
E85 is a great idea, I don't know much about it. For endurance racing I believe the fuel consumption is higher so that might be a problem for our current 1.5hr stint strategy, the cell just isn't big enough. I'd also have to check the bladder in my cell and make sure that it's ok to use with alcohol.
nice build , cant wait to see the final results
09-28-2010, 08:49 AM
#38
Hey Guys,
Sorry for the lack of updates.
It turns out the flywheel had cracked at the starter / trigger
So that is what was chewing up the sensors. Repaired the flywheel and the car has been running well since then! Set a few lap records at local time attacks, and am on my way to a 1:26 at Mosport.
We just finished modifying this upper plenum which found some extra power, comparable to the carbotron intake. Car is now making 331whp, the hood closes and it has a throttle body - unlike some of our other tests! So this is legit horsepower, although I was wishing with the compression I would be at 340whp by now.
Short Fly-by Video:
Sorry for the lack of updates.
It turns out the flywheel had cracked at the starter / trigger
So that is what was chewing up the sensors. Repaired the flywheel and the car has been running well since then! Set a few lap records at local time attacks, and am on my way to a 1:26 at Mosport.
We just finished modifying this upper plenum which found some extra power, comparable to the carbotron intake. Car is now making 331whp, the hood closes and it has a throttle body - unlike some of our other tests! So this is legit horsepower, although I was wishing with the compression I would be at 340whp by now.
Short Fly-by Video:
