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3.1L Dyno results...Thoughts?


steve260z

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Sorry to have to agree with Xnke but power is made in the head. I have no idea how much money I have in my motor/head although it is significant. Though I have never had my car put on a dyno I can tell you this. A Rebello built 2.8 L dynoed at 289 hp car with 3.90 limited slip and same transmission when run agents my Pettersen built 3.1 L with E88 head and tons of custom work, with same Robello cam although I run a 3.70 rear end and I have 0.3 L more displacement. My Pettersen 3.1 L smokes the Rebello 2.8 L. Now in Rebellos defense this 2.8 L was just a motor he had sitting on the shelf for sale nothing special. These two cars are very similar although my car has a heavy sound system 1900 watts and lots of Dyno Mat Extreme sound deadening. In My opinion your 40s and stock P90 head are starving the motor for air. You need head work and 45.

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 A Rebello built 2.8 L dynoed at 289 hp car with 3.90 limited slip and same transmission when run agents my Pettersen built 3.1 L with E88 head and tons of custom work, with same Robello cam although I run a 3.70 rear end and I have 0.3 L more displacement. My Pettersen 3.1 L smokes the Rebello 2.8 L. 

Curious how to quantify "smoke".  Is this butt-dyno, real dyno, 1/4 mile times?  11% more displacement, but much more than 11% increase in "power".

 

The OP's engine seems to be basically an enlarged stock ZX-style engine (flat top with P90 head) with a Schneider Stage 2 cam and a 9.9 CR.  But the 11% increase in displacement doesn't seem to be giving the 11% increase in power.

 

Just looking for details.  Of course, the old dyno vs. dyno variance factor comes in to play also.

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Curious how to quantify "smoke".  Is this butt-dyno, real dyno, 1/4 mile times? 

As stated I have never had my car dynoed but I have been the driver in my car when we compared the two cars side by side. In this case the 0.3 L advantage helps. Somewhere as expected the 3.1 L  is making more horse power/ torque than a 289 hp motor that is dynoed, 289 hp is just a number.  My car consistently out accelerates my friends 2.8 L. that has the number 289 hp attached to it at the crank. This demonstrates that two well prepared motors with head work, the same cams, and 45s make similar power with the 3.1 L making more as would be expected.  

 

However, in Steves 260z with the same 3.1 L displacement it is not making within 100 hp at the wheels of the Rebello 2.8 L at the crank.  A 2.8 L making 289 hp is nothing to be embarrassed of. I would think Steve would be happier with a number at the wheels of 230 hp. In Steve's case it sounds like he is disappointed in the numbers made and I think you need to look at air flow. It could be a combination of carbs, cam, and/or head. Steve may not be interested in the $ per cubic hp numbers but it sounds like he would like to get his motor as dialed in as he can. Steve has gone the extra mile to build 3.1 L bottom end which usually indicates someone looking for more power, but limited the top end area of his build. This is an area that is easier to return to and build at a later time if he wishes.

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Well put. Yes, I can always go and have head work done. That's exactly why I didn't do it during the build.

For comparison, I've attached the dyno results of the car after me. 280z with Schneider Cam, bored 40 over and other mild modes.

This car maintains power up to about 5,500.

post-8997-0-66957300-1398629580_thumb.jpg

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I think part of the problem is ignition too, but I wouldn't expect an extra 100 hp from fixing it.

 

Read zredbaron's thread. He went from a 3.1 that made 150 whp or something like that to one that made 280 something and documented the whole thing.

http://forums.hybridz.org/topic/24798-na-31lhead-camshaft-questions-no-shortcuts-max/

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Definetly sounds like somethings going on like a miss or something. You need to install an o2 sensor to eliminate fuel issue. Could be running lean at top end. I'm probably running running your numbers with my L24.

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What are your main jet, tubes, and air corrector sizes on your webers? Watching the video it looks like it could be a jetting issue with the popping sounds on the exhaust. Agree'd on the head porting, your going to unlock a lot of power there, but shouldnt die off like that... leads me to believe either a jet problem or ignition issue.

Edited by AZGhost623
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