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Senior Privileged Member
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Discussion Starter #1
I've been posting about the mods that I have had done at MTI Racing.

So far those include:

Dynatech Supermaxx headers
Custom true dual cat-back exhaust (MTI Dual Shotgun Exhaust)
Rush air filter
Dyno tuning by MTI using EFILive

Here's the actual current dyno curve.

The increase in "peak" horsepower is "only" 20. But, if you count squares between the "before" and "after" curves in the 3600 to 5800 range (the range which both before and afer dyno runs covered), you will find that the AVERAGE increase in HP was 30 hp, and the AVERAGE increase in torque was 34 ft lb.

The 4.56 gearing I am running does not of course add any horsepower, but by compressing the gearing by 22% over stock, it GREATLY improves acceleration, especially in the 0 to 60 range.

Jim G
 

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Resident Rocket Scientist
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Chart

Jim,
Can you explain the step in the torque curve at 3500 to 3600 rpm. What's with the start points of the curves - why the higher rpm start point on the second set of data?
Aside from that the torque curve really got fattened up. The higher gears must be fun, just roll onto the throttle and you're flying!
 

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Las Vegas Mob
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Geeezz! That torque curve is monster wide and at a low enough RPM that it is readily available! Very impressive for an atmosphere breathing mill. With your 4.56's you must have a very "happy" ride :thumbs . In your situation (normally aspirated), to get that large a torque jump at that low an RPM range generally requires getting a serious handle on pumping losses which proves that the folks at MTI know a thing or two about intake/exhaust issues. I am now officially jealous!! :) :)
 

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Discussion Starter #4
hdflstf said:
Jim,
Can you explain the step in the torque curve at 3500 to 3600 rpm. What's with the start points of the curves - why the higher rpm start point on the second set of data?
Aside from that the torque curve really got fattened up. The higher gears must be fun, just roll onto the throttle and you're flying!
That step is not "real". It's the power enrichment routine of the VCM kicking in when Reese applied full throttle. Reese says he needs to figure out why the VCM is taking too long to react.

Because this is the first SSR he has taken on, he has not yet learned all the tricks he has about the C5s and C6s. He also has to figure out how the torque management works on the SSR program, as we believe it is set VERY conservative.

When I read the descriptions of what the commerical prepackaged microtuners are doing, I am pretty certain that they are tightening shift times, increasing shift pressure, increasing WOT shift rpm, and altering the torque management limits, all sometimes rather aggressively - more aggressively than either Reese or I want to go. BUt, Reese has already tightened the shifting somewhat, and raised the shift rpm, but not as high as the microtuners. The torque management needs more study.

The shifting, the torque management, and the high rpm performance need more work. The low rpm and mid range rpm response is now pretty strong and very satisfying. It's almost like a slot car changing lanes at 60 to 75 mph without a downshift (2200 to 2750 rpm with my 4.56 gearing!).

The sound is a BIG improvement. Had another incident yesterday. A driver in the next lane was gesturing persistently for me to roll down my window. When I did so, he simply said "THAT's what a V-8 is supposed to sound like."

Jim G
 

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Discussion Starter #5
I almost forgot. Most dyno runs done by MTI and other shops start where the "after" run in this chart starts. (3600 rpm) The only reason we have lower rpm data for the before run is that I remembered to specifically ask Reese to get it, as I needed it for my modeling software.

To get it, Reese had to defeat the automatic's downshift feature. With his OLD dyno software, he had a routine to do that. To read the SSR's VCM however, he had to use new software that he is not yet familiar with (EFILive), as the old software (LS Edit) does not yet offer on-vehicle VCM programming for the GM trucks. So, with the EFILive software, he had to let it downshift, which is why we got both the delayed power enrichment effect and higher rpm start for the chart.

We are in "learn" mode on this vehicle and with this software.

By the way, some of the nice things about EFILive software are:

- It reads a VCM regardless of what software modified it, provided it has not been locked with a password

- It will rescue most "wiped" VCMs that other software has given up on

- I can buy a personal copy that comes with licensing for 4 VINs

- I can upgrade to a workshop copy for $150 more, which will give me the ability to lock the VCM, so that a Chevrolet dealer does not reflash without my prior permission.

- I can keep mutiple versions of my VCM programming (factory stock, pre MTI, and all MTI versions) on my laptop, and restore and remove from the VCM anytim I like.

I have not needed to buy my own copy yet, but plan to later. In the meantime, Reese has his own licensed software and cable. Extra licenses (one for each VIN) are $100 each.

Jim G
 
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