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Kirkster

Moving the Torque and HP curve

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Ok,  Brief background.

 

First Pull is from a few years ago with the group buy SENZA PARI intake.  We figured the short intake runners killed the Torque on the motor.

 

Second Pull is from this spring with a rebuilt .40 over motor as the old motor dropped compression on the #4 cylinder and had to be rebuilt.  

 

The motor is an N42 with N42 head and is completely stock with the exception of the .40 overbore.  

 

We are readying a new intake which will be port matched to the head and also will have had the runners opened up.  The big issue we have with the current intake is this is a webbed EGR intake  and the intake log is necked down for the last 2~3 cylinders and we are not sure if that is impacting the flow.  So we are going to a non webbed non EGR intake that is the same diameter the whole way down the log.

 

IMG_0326-e1502371595368.jpg

 

The real issue that we would like to solve is moving the HP and Torque a bit further along in the RPM range as the Torque peak is faith at 4400RPM and the HP peak is at 5000RPM.  we expected it to not peak at such a low RPM.

 

We are also thinking an adjustable Cam Pulley might help us move the peaks.

 

Any thoughts??

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Was the Senza intake used on both pulls?  Just wanted to clarify that the only difference was the rebuilt w/ .040 over.  It sounded like you went back to webbed EGR intake, but you stated the fresh bottom end was the only difference -- just making sure I read that correctly.

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Posted (edited)

Was the Senza intake used on both pulls?  Just wanted to clarify that the only difference was the rebuilt w/ .040 over.  It sounded like you went back to webbed EGR intake, but you stated the fresh bottom end was the only difference -- just making sure I read that correctly.

I went to the webbed EGR intake due to the short runners on the Senza intake killing the torque on the motor.  This advice was from a guy that was racing and crewing for them in the good old days

 

Run file 12 is the Senza intake Run 44 is the webbed EGR intake.  The longer runners definitely brought the torque back...

Edited by Kirkster

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With a stock cam arent you close to the limits of moving the curve. You could get an adjustable cam sprocket and start retarding the cam timing to see where that takes you.

We are probably ordering an adjustable cam sprocket soon.  Just putting a toe in the Hybridz waters on any other ideas...

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Posted (edited)

We are probably ordering an adjustable cam sprocket soon.  Just putting a toe in the Hybridz waters on any other ideas...

...so is this the _same_ motor rebuilt and bored 0.040" over, or is it a different motor/head?  Your description sounds like it's two different motors, but it's not clear.  Do you know what the cam/cam timing was for both motors?  It's possible that the cam was advanced on the Senza motor with respect to where it was timed on the new motor, which could also result in torque curve differences.

Edited by TimZ

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...so is this the _same_ motor rebuilt and bored 0.040" over, or is it a different motor/head?  Your description sounds like it's two different motors, but it's not clear.  Do you know what the cam/cam timing was for both motors?  It's possible that the cam was advanced on the Senza motor with respect to where it was timed on the new motor, which could also result in torque curve differences.

Yes it is the same motor/injectors/megasquirt with just the intake manifolds being changed along with the rebuild and overbore... Don't know what the cam timing is as the motor was previously factory stock and we did not check the cam timing when the rebuilt motorwent back into the car.

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Yes it is the same motor/injectors/megasquirt with just the intake manifolds being changed along with the rebuild and overbore... Don't know what the cam timing is as the motor was previously factory stock and we did not check the cam timing when the rebuilt motorwent back into the car.

 

The title of your thread should really be about why a person needs to collect information before they make changes.  You're starting from scratch now and can't really draw any conclusions about the intake manifolds or engine combinations.  You're really just talking about what you should have done.

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The big issue we have with the current intake is this is a webbed EGR intake  and the intake log is necked down for the last 2~3 cylinders and we are not sure if that is impacting the flow.  So we are going to a non webbed non EGR intake that is the same diameter the whole way down the log.

 

The real issue that we would like to solve is moving the HP and Torque a bit further along in the RPM range as the Torque peak is faith at 4400RPM and the HP peak is at 5000RPM.  we expected it to not peak at such a low RPM.

 

We are also thinking an adjustable Cam Pulley might help us move the peaks.Any thoughts??

 

There are really only three 280Z(X) manifold types.  Are you talking about 280Z versus 280ZX?  The webbed 280Z has the same runners as the non-webbed, I believe.  1978 versus 1976.

 

What position is the cam sprocket at?  There's only three holes.

 

Besides the position of the power on the RPM curve, you also made less with the SP manifold.  The premise of the manifold was supposed to be higher numbers overall, besides the shininess.  Beside that, many did not fit right.  How did you get yours to fit?  Could be some misalignment of the runners. 

 

As you restart the development work, make sire you collect good precise information.  

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There are really only three 280Z(X) manifold types.  Are you talking about 280Z versus 280ZX?  The webbed 280Z has the same runners as the non-webbed, I believe.  1978 versus 1976.

 

What position is the cam sprocket at?  There's only three holes.

 

Besides the position of the power on the RPM curve, you also made less with the SP manifold.  The premise of the manifold was supposed to be higher numbers overall, besides the shininess.  Beside that, many did not fit right.  How did you get yours to fit?  Could be some misalignment of the runners. 

 

As you restart the development work, make sire you collect good precise information.

 

 

My SP manifold was a webbed manifold thus the alignment issues that hampered the SP non webbed manifolds was not there. The short runners killed the torque on the SP manifold. If I go turbo that manifold will go back on. It just does not perform well NA.

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 The short runners killed the torque on the SP manifold. If I go turbo that manifold will go back on. It just does not perform well NA.

 

So how long are the runners in the SP manifold, and how long are stock?

 

Besides the .040" overbore number, there's just not much that's been quantified.  You don't have any numbers to work with.

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An adjustable gear may move it up somewhat, but there likely will be a torque tradeoff made (it will be peakier, loss at the bottom). There is only so much you can do with the L28 cam which peaks at around 5300. An L20A cam, or L26 C cam was the hot ticket from my recollection. They will pull all the way up to a power peak at 6500. 

 

The difference in the two, you see the characteristic HP curve is very similar, timing will move it left or right, not up or down. The torque curve is the same, it will move SLIGHTLY upward, but there will reach a point that the bottom end just go away completely. The torque is VERY dependent on proper timing events. It will move a LITTLE, but it will get peakier. The HP will move somewhat left or right...we are talking 2 to 4 degrees max.

It appears run 12 had a better, wider torque curve, and the HP curve was  proper. The Red Traces though higher and WAY to early, and my bet is you will be able to move them where the blue traces are, without affecting much on the bottom end, the torque falls off WAY to early on the blue traces as does the HP. I think the timing is slightly off, maybe 2 degrees. Get that adjustable cam gear and get the events proper...or just reference it, and then go 2 degrees one way, and 2 degrees the other. That will show you which way will gain you what you want.

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