secondarries

[Tyler Townsley]

Originally Posted by XfireZ51

Graham,

First of all, welcome! Super to have your one of a kind perspective.
Looking at the curves, was anyone ever able to explain that sag in the torque curve between 4-5Krpm that seems so characteristic of the LT-5.
I know Marc H. can show you graphs of variously modded LT-5 but that sag shows up on each one of them. Just curious.
BTW, how about a thread on the 2nd Gen LT-5 build?

Cheers.

Talked to Geoff today and he confirmed what I always thought. The dip you see is a combination of the 1 injector going into saturation and the 'turning on' of the 2 injector mode. I would be interested in seeing a run with the 2 injector graph right behind a all in graph on the same motor. Apparently the crossover point causes the motor to run a little lean in that part of the calibration.

Tyler

[grahambehan]

Tyler,
OK we have already confirmed that the LT5 goes into 16 injector at WOT, so lets think about that? There are many phenomina that influence the characteristics of an engine, ie the fundamental shape of the curve, P/T switching is not one of them, in this instance

Graham.

[Tyler Townsley]

Originally Posted by grahambehan

Tyler,
OK we have already confirmed that the LT5 goes into 16 injector at WOT, so lets think about that? There are many phenomina that influence the characteristics of an engine, ie the fundamental shape of the curve, P/T switching is not one of them, in this instance

Graham.

OK Todd has a calibration mod that can be used in a stock motor that can be used to test that. It pulls the secondary throttle blades open and goes 16 injectors on startup. It changes nothing else in the calibration, run that back to back vs a stock calibration and see what happens.
In the stock configuration going WOT does not enable an instant 16 injector secondary's open mode there are a series of check points that have to be met before going to the next calibration configuration and into the final PE table.

If not that then its cam design? Ie the lower rpm profiles are such that its engineered for a leaner mixture and it gets more aggressive as the rpms elevate with a transition point where the motor is slightly under fueled.

Its got to be in the fueling, calibration or cams.

Tyler

[grahambehan]

Originally Posted by Tyler Townsley

OK Todd has a calibration mod that can be used in a stock motor that can be used to test that. It pulls the secondary throttle blades open and goes 16 injectors on startup. It changes nothing else in the calibration, run that back to back vs a stock calibration and see what happens.
In the stock configuration going WOT does not enable an instant 16 injector secondary's open mode there are a series of check points that have to be met before going to the next calibration configuration and into the final PE table.

If not that then its cam design? Ie the lower rpm profiles are such that its engineered for a leaner mixture and it gets more aggressive as the rpms elevate with a transition point where the motor is slightly under fueled.

Its got to be in the fueling, calibration or cams.

Tyler

Tyler,
You guys are "Really" too funny! If you press the right pedal at 1000 rpm the PT are open, so if, as the original question was about, there is nothing to do with PT opening what it is about is tuning resonances, whatever that means, google it.

Take Care

Graham.

[XfireZ51]

Originally Posted by grahambehan

Tyler,
You guys are "Really" too funny! If you press the right pedal at 1000 rpm the PT are open, so if, as the original question was about, there is nothing to do with PT opening what it is about is tuning resonances, whatever that means, google it.

Take Care

Graham.

Graham,

Yes since the dyno graphs are at WOT, both injectors are obviously operational. By your response I take it is the fingerprint of the induction system harmonics.

[grahambehan]

Originally Posted by XfireZ51

Graham,

Yes since the dyno graphs are at WOT, both injectors are obviously operational.

No, if your talking about the dyno graphs I posted, the curves are PT open and PT closed, just trying to dispell the myth as potificated by an earlier post.

Graham.

[XfireZ51]

Originally Posted by grahambehan

No, if your talking about the dyno graphs I posted, the curves are PT open and PT closed, just trying to dispell the myth as potificated by an earlier post.

Graham.

I was alluding to my own dyno graphs or ones that Marc H has in his shop. The graphs you posted reminded me of that.

[grahambehan]

Originally Posted by XfireZ51

Graham,

Yes since the dyno graphs are at WOT, both injectors are obviously operational. By your response I take it is the fingerprint of the induction system harmonics.

Sorry, obviously didn't read the question enough, my bad. There are many things that influence the characteristics of the engine. Fundamentaly we design the engine from the combustion chamber out. The variables include, zip tube length, plenum volume, runner length, runner gemetry, port length, port geometry,port volume, combustion chamber, exhaust geometry, valve timing, exhaust runner length, cam profile, timing etc. If we look at the modifications the aftermarket has done to the LT5 the fundamental characteristics of the engine have not really changed that much, so the shape torque curve, or it's relationship to BMEP, versus engine rpm will not change that much either. Now , obviously the peaks occur at different rpm, but the rest is what it is, without major geometry and architecture changes.

Graham

[tf95ZR1]

Nevermind............

[grahambehan]

Originally Posted by tf95ZR1

Ok, I guess I get to try and figure the graph out myself. It looks
like the primaries add a lot at the low end, but then fall. That's
when the secondaries kick in to haul a**. But deleting the
secondaries shouldn't affect the primaries at low RPM if the A/F is
adjusted, right? Are you saying it "bogs" at low RPM?

No, I'm not quite sure what takes figuring out. The primary port is a swirl generator and port throttles closed at low rpm = more torque. C0mbination of port geometry and cam profile. At higher rpm both open = more torque * 5252 = more power.

Graham.