secondarries

[RHanselman]

Originally Posted by Paul Workman

My stock 90 LT5 WOT (w/ secondaries) torque vs. WOT after porting both runners and SPTs removed.

As Pete said before, I too can't see where torque was lost on the low end - at least not above 2000 rpm...



(Excel graph of data taken from separate dynos, SAE corrected.)

YMMV...

P.

Paul,

What we need is a comparison of the stock car with the GM ECM with and without the secondaries and then with the MS. If their tail is true then you'll see more TQ with the new ECM and the secondaries.

Cheers,
RH

[Paul Workman]

Originally Posted by RHanselman

Paul,

What we need is a comparison of the stock car with the GM ECM with and without the secondaries and then with the MS. If their tail is true then you'll see more TQ with the new ECM and the secondaries.

Cheers,
RH

Yep. Looking fwd to it. Hope took see the presentation @ BG!

[Pete]

Thanks for posting the graph Paul.

If you notice it has 25 more torque across the whole graph w/no secondaries.
You guys are saying from 1000 rpm it would spike up and at 2000rpm it smooths out.
So the graph would look like this.

[RHanselman]

Originally Posted by Pete

Thanks for posting the graph Paul.

If you notice it has 25 more torque across the whole graph w/no secondaries.
You guys are saying from 1000 rpm it would spike up and at 2000rpm it smooths out.
So the graph would look like this.

Nope, I'm not saying anything. Just passing along a data-point that the MS guys experienced during tuning my stock car. I'd like to find out if it's true.

Pete, I think you meant: "if you notice it has 25 more torque across the whole graph w/no secondaries AND PORTING"... By the graph it's unclear as to what mod caused the increase in TQ. Port could have made it all or they could have a ratio.

Paul, go out and put your secondaries back in real quick like and get us some numbers! In jest of course...

Cheers,
R

[Pete]

Ron,sometimes my brain is faster then my one finger typing.

I'm just speaking in general,not directly to you, just throwing out the way a stock LT5 chip programing works.

Paul don't worry you don't have to put your secondaries back in to find out.

From the old thinking bigger ports slow down velocity then Pauls ZR-1 and every other top end ported lt5 should loose more TQ/power.

Like i said in my previous post a pure stock Z secondaries are open anytime you go WOT no matter the RPM.

Stock LS3 has 260cc intake runner with no secondaries drives just fine,some CnC them to 275cc, stock LT5 head is a whole lot less from what i can remember 210-215 it shouldn't have any drivability issues we also have better valve angle.
Like i said i'm putting this stuff out from memory it's been a while since i did the R&D on the LT5 stuff (10 years).

The LT5 was ahead of it's time heck most LS stuff today came from LT5 development.
Pete

[Hib Halverson]

It is true that the port throttles are open anytime the engine is is at WOT, however, anything below 90% TPS (ie: "almost WOT") that's not the case. Below 90% TPS, SPT opening strategy varies according to TPS and RPM.

Stock or near stock 350s need port throttles to have good driveability and good torque at high part throttle in the lower RPM ranges.

Highly modified 350s may not need them and drag race-only 350s don't need them. Also, any engine modified by someone who doesn't give a s@@t about performance/drivability other than at WOT/high-rpm doesn't need them.

368s which are otherwise stock or near stock may not need them.

Bigger than 368s...rip 'em out.

If you're takin' 'em out, and you're actuators are good, send them to me.

[Paul Workman]

Originally Posted by Hib Halverson

(snip) ...any engine modified by someone who doesn't give a s@@t about performance/drivability other than at WOT/high-rpm doesn't need them.

Hib... with all due respect... you're dead wrong about this. You're basing your statement on what "someone" has said or written, methinks, but certainly NOT on actual experience or testing! Theory goes just so far, and then truth is where you find it.

It's all in the tuning. May I suggest you put whatever tech references you're referring to aside and acutally drive one, so modified. I think you'd have some about what "some" have said or predicted about performance/drivability up to that point.

Incidently, the second generation LT5 under development did NOT have dual runners. Instead the runners resemble the siamesed Lingenfelter runners; i.e., one BIG oval port. Evolving from dual runners to a single runners, while maintaining the 4-valve head suggests (to me and others) some performance gain could be had without giving up performance and drivability. This is something perhaps suggested by the Lingenfelter mod success, but for certain has been demonstrated over and over again by those that have removed the secondaries (essentially reverting to a single port) in favor of drivability and performance. If they had it to do over, would Lotus have gone with the dual set of runners, etc? I wonder...

[LancePearson]

Most of us don't spend a whole lot of time at 750 to 1500 rpm so pulling them out is pretty much a non issue and if combined with porting and relieving and bigger exhausts with tubes seems to me the engine will breath better and be easily up there where the Lotus dyno tests were at a minimum if not well over that. If and when I open my plenum I may just go ahead and pull the secondaries to simplify the engine's mechanics entirely.

[XfireZ51]

Hib,

I wonder how much of the "stock motor needs secondaries" conventional wisdom is a result of removal but not addressing the tuning properly. Anecdotally, the problem should be exacerbated by top end porting of an otherwise stock motor.
More air by increasing volume should negatively affect flow velocity on the low end. And that should demonstrate itself as a loss of low end torque.
Perhaps the addition of freer flowing exhaust (re: headers) which tend to accompany other mods, may mitigate the effect of greater volume. How much of the "loss of low end" is SOTP instead of data driven? My own personal experience has been that porting the top end, and having secondaries come on just after idle has increased torque throughout the rpm range and I could post dyno sheets showing that. Most tuners will tune for WOT, but the process of tuning for part throttle is much more time consuming and involved than WOT.
Which is why it's not done. Having looked at calibrations from other tuners, I can tell you that the stock calibration is hardly modified if at all. And in fact, it needs to be modified quite a bit.
So my point is that we can't be sure how much of the low end loss is due to improper tune rather than strictly a result of removing secondaries. Maybe we'll never know.

[Hog]

Originally Posted by Pete

Hog we are saying the same thing,about old technology what they had to do with what they had at the time.

We are also agreeing about technology has gotten better,performance has been vastly improved from 20-30 years ago and tuning devices have been improved.

I might have to disagree on this i don't think there is a loss below 1500 rpm if so what are we talking about? Again tuning comes into play.

If you as much as graze my gas pedal heck if you sneeze on it jumps to 1500 i will put my throttle response over any stock Z's thottle response.

I do have to say that i do idle at 900 with the big Stage III intake cams .242 .450 with .224 .420 exhaust in a 350ci motor.

When i drive my Z to Bowling Green(highway) i basicly leave her in 6th anything at or above 45mph she's good anything lower i'm at idle speed.

Pete

Cool Pete, sounds great. I was just following Mark Haibeck's lead about the under 1500rpm torque loss. I'm not sure, but maybe he was talking about removing the secondaries and then tuning for the new injector operations and not tuning to recover that under 1500rpm torque loss(if there is a loss at all)

You comments anout your highly modified/cammed 350 LT5 is very encouraging. It sounds like you car is very very driveable. I wouldn't enjoy a car that required excessive pedalling in order to pull away from stoplights.

I agree 100% with the ECM tuning. Having the proper calibration for any combo is paramount.

Sounds like removing secondaries along with "good" ECM calibration will not negatively affect drivability in the slightest, with only benefits being realized due to the improved calibration when compared to the stock late 80's early 90's calibrations.

I know that in the mid 90's OBD2 calibrations there are marked gains to be had from fueling alone, then add in the gains realized from Torque Management recalibration, makes for some very thrilling improvements in acceleration.
In the middle/late 2000's, acceleration gains from fueling/timing are much smaller, with a majority of gains coming from recalibrating PCM/ECM/TCM torque managemnt functions. In other words, in modern platforms there is less power to be found from tuning, as OEM calibrations are getting very precise. Conversely there is a lot to be found from 80's early 90's platforms.

I wish there was a way to pull the secondaries, but still allow the Power Key to function. Like could we pull secondaries, allow both injectors to run all the time, but when needed, only use 1 single injector when reduced power is requested with the key? My feeling is no, because that would result in excessivley lean mixtures with both intake runners providing air even with just the single injector functioning.
Is there any way to enable say a 4500rpm rev limit using the Power Key?

peace
Hog