Can I get TBI off idle torque with my vortech?

[Batass]

TBI engines suit my driving style better in a truck, how can I get that torque back in my 99 5.7? Is it lost without the swirl port heads or is it tuning?

[Batass]

This seems like an easy question

[randeez]

get some gears

[Batass]

Gears aint the fix. My 88 with 2.73 gears was torquier than this thing.

[silverado_lover]

Don't be afraid of the gas pedal

[Batass]

I dont like to drive my truck like its a honda. GM removed the snappy tq bc people dont know how to use the throttle. I want it back. Stop wasting my time with stupid answers. If I want worthless advice ill go to advance auto.

[silverado_lover]

Get tune, remove all TM and see what happens

[Batass]

Will that give me more off idle torque? What about the lip on the throttle blade? I removed it from an s10 and it helped but this has a smaller lip.

[silverado_lover]

Well TM stands for torque management so I'm going to guess it will be a step in the right direction

[Batass]

Yes I know what TM stands for and I believe it only affects torque during shifts and abuse mode. I want off idle.

[Doober]

You can add timing in low rpm/high vacuum areas and it should bring it up. I was able to add quite a bit when I put Vortecs on my 383 and the SOTP feeling was negligible.

Don't feed the trolls btw :lol:

[BlacK20]

well with a vortech supercharger, you should have tons of torque...

[Batass]

Doober you say adding timing didnt help the sotp feel? I think the off idle tq I love and miss so much is in the swirl port heads. I have a vortech blower but its on the camaro. I just want this thing to react like it has a 350 not a damn 2.8.

[Doober]

I just meant it was similar to the low end it had with swirl ports. It may have just been a placebo thing but overall low end torque is still great, given that mine is a 383. I have a minor vacuum leak I think, it idles higher than the ECM commands above 12-14º or so, the throttle shaft needs bushings. If I set low end timing a little more aggressively it will spin through 1st with 3.08s and 28" tires.

[Batass]

Im sure your low end is real nice with 40 more ft lbs! Looks like im pickin up efi live....

[silverado_lover]

well with a vortech supercharger, you should have tons of torque...

First thing I thought of when I saw this thread the first time :lol:

[Fast305]

Im sure your low end is real nice with 40 more ft lbs! Looks like im pickin up efi live....

Not sure why yours doesn't have low-end. Even with the stock untouched throttle body with nothing more than a little DIY tuning, the Vortec 350 in the Express has jumpy throttle response. Lack of AE fuel is part of the issue with a Vortec setup. That and the stock cam is nothing to write home about. I gained power everywhere with a production LT4 cam. This has Doug Thorley Tri-Y headers, LT4 cam, S10 torque converter, and DIY Tuning.

http://www.youtube.com/watch?v=7SgptElOCpY

What you don't realize is this beheamouth is 6,100 lbs and only has 3.42 gears. Its a heavy conversion van with leather seating, power tri-fold rear seat, TV, VCR, rear Radio, Rear A/C, lots of heavy wood trim, heavy carpeting throughout, extra door panels, among other things. A stripped down cargo van would be a second or two quicker 0-60.

[Batass]

Just the guy I was looking for. Ive read a bunch of your TBI stuff years ago. My truck moves well if I hammer the throttle, it just doesn't have that responsive grunt like my TBI trucks have had. Every vortec Ive driven feels the same. v8s and v6s compared to the tbi motors. Is AE acceleration enrichment? The stock cam really doesn't look bad for the power range I like in a dd truck. It rarely sees over 3000 rpms. I really don't want to do anything wild to it, I still have my camaro to finish and just bought a 91 conversion style suburban thats getting a cummins diesel/dodge frame swap....

[Fast305]

Just the guy I was looking for. Ive read a bunch of your TBI stuff years ago. My truck moves well if I hammer the throttle, it just doesn't have that responsive grunt like my TBI trucks have had. Every vortec Ive driven feels the same. v8s and v6s compared to the tbi motors. Is AE acceleration enrichment? The stock cam really doesn't look bad for the power range I like in a dd truck. It rarely sees over 3000 rpms. I really don't want to do anything wild to it, I still have my camaro to finish and just bought a 91 conversion style suburban thats getting a cummins diesel/dodge frame swap....

Honestly I think what you are describing to me fits more along the throttle cam and blade restriction fall. Less throttle opening for a given pedal travel. TBI setups without throttle cams give very linear opening and this gives a very responsive pedal feel. The Vortecs feel "DEAD" in this respect because the same pedal movement gives much less throttle area for air to move through, less air is less power. Even a 95 C1500 with a 305 can feel peppy despite being a dog. Removing the restrictor on the butterfly helps.

Also disconnect the EGR and see if the response improves. The linear EGRs are plagued with issues that allow them to open substantially quicker than they are being commanded to open. This causes a tip-in hesitation and in more severe cases a bog on take off. My Express had a hesitation that started and remained for over a year that I never could figure out and one day popped an EGR code. Replaced the valve and instantly it felt like I gained 100 ft/lbs on tip-in.

The TBI heads make about 10-15 ft/lbs more from low engine speeds and only fall off above 4,500, but I don't think that is what you are feeling.

AE = Acceleration Enrichment

Also take not that PE, power enrichment is delayed until 90% throttle in the stock Vortec tunes for some crazy reason. I remapped my PE on everything to operate more like the power valve of a carb and that drastically helps throttle response under load. Pull hills in OD with the converter clutch locked opposed to downshifting to 3rd kind of difference.

[randeez]

finally... someone that knows how to make every truck feel like it has a tbi

[Batass]

Thats some golden information Fast, thanks. If you wrote a book on GM EFI, I would buy it in a heartbeat. If it was fly by wire, Id just turn the sensitivity up. Is there a way to make the egr open at a higher vacuum without throwing a code?

[Fast305]

finally... someone that knows how to make every truck feel like it has a tbi

Basically you either need a bored/ported throttle body from someone like CFM Tech or modify the throttle linkage with a throttle came that is a perfect circle. You can use some of the V6 or 4 cylinder throttle cams as they have a different opening rate.

You should feel my 5.7 Hemi Ram, lol. With a non drive by wire setup on a 4.7 ecm, 85 mm cable operated throttle body, small custom grind comp cam, milled & ported heads, BBK equal length shorty headers, single 3.5" exhaust, APS 3,000 stall with a 2.6 STR and 4.56 gears it is scary responsive. Now I just try to make everything respond like it. My Titan comes close now with 383 RWTQ on a mustang dyno and over 350 RWTQ @ 2,500 through a 5spd auto with a 4.00:1 first gear and 3.36s out back.

[Fast305]

Thats some golden information Fast, thanks. If you wrote a book on GM EFI, I would buy it in a heartbeat. If it was fly by wire, Id just turn the sensitivity up. Is there a way to make the egr open at a higher vacuum without throwing a code?

With HP Tuners or EFI Live you get control of the whole EGR table. It is an table that bases % EGR opening with RPM and MAP. I typically delay the opening around town at lower rpms and higher loadings, but really crank up the EGR at ~1,800-3,000 rpm at light loading, lower kpa. Also unlike the factory tunes, I leave alot of EGR in the 3,000-1,200 rpm range at 0-20 KPA range, thats to help eliminate pumping losses and lets you cost longer with your foot off the throttle. The reason I don't go higher rpm, is so that I can downshift into 2nd at 60+ mph and get engine braking if I need it.

[kendogg]

I'm interested in this too, especially since I plan to tow with mine.

My parents had a '95 1500 extended cab Z71 brand new, and with 3.73's (stock) out back, it would just bake the tires off. My '97 2500 2wd at WOT off the line will barely spin the tires. I've been told the stock cam is hard to beat for a towing application, is this true?

[Fast305]

I'm interested in this too, especially since I plan to tow with mine.

My parents had a '95 1500 extended cab Z71 brand new, and with 3.73's (stock) out back, it would just bake the tires off. My '97 2500 2wd at WOT off the line will barely spin the tires. I've been told the stock cam is hard to beat for a towing application, is this true?

Your 2500 should have the 4L80E transmission rather than the 4L60E. The 4L80E has a 2.48 first gear ratio compared to the 4L60E's 3.06 first gear. 2nd gear is also lower at 1.63 on the 4L60E vs 1.48 of the 4L80E. This means the 4L60E will jump right out there. The 4L80E also takes an additional 5% or so power to turn than the 4L60E, which gives you even less performance, but more durability. Gear ratio alone, it would take you a 4.56 final drive to get the same off the line jump as a 4L60E and even if you change the ratio the 80E still eats more power.

I have always felt the stock cam is a weak little stick. I never liked it in the Express to say the least. I always hated the feeling of driving along at 55-60 MPH, mashin the throttle, the transmission kicking down to 2nd gear, the engine reving up to 4,500+ and NOTHING except noise. The LT4 cam that is in my Express doesn't stop pulling until it is well over 5,500 rpm. It pulls around the 6,100 lbs Express in OD uphill just fine. Its not like you are going to be towing 5,000+ lbs in OD anyway. MANY aftermarket and even GM grind cams come on stronger than the stock cam, well below the RPM that you would be running while towing in 3rd gear. 5.7 Vortec can sing 3,000 rpm @ 70 pulling 5,000+ lbs all day long. Get into the mountains pulling a heavy load and you are going to be screaming 4,000+ rpm in 2nd anyway. With an automatic transmission you want a cam that makes power from 1,800-5,400 for a Vortec truck.

[kendogg]

Your 2500 should have the 4L80E transmission rather than the 4L60E. The 4L80E has a 2.48 first gear ratio compared to the 4L60E's 3.06 first gear. 2nd gear is also lower at 1.63 on the 4L60E vs 1.48 of the 4L80E. This means the 4L60E will jump right out there. The 4L80E also takes an additional 5% or so power to turn than the 4L60E, which gives you even less performance, but more durability. Gear ratio alone, it would take you a 4.56 final drive to get the same off the line jump as a 4L60E and even if you change the ratio the 80E still eats more power.

I have always felt the stock cam is a weak little stick. I never liked it in the Express to say the least. I always hated the feeling of driving along at 55-60 MPH, mashin the throttle, the transmission kicking down to 2nd gear, the engine reving up to 4,500+ and NOTHING except noise. The LT4 cam that is in my Express doesn't stop pulling until it is well over 5,500 rpm. It pulls around the 6,100 lbs Express in OD uphill just fine. Its not like you are going to be towing 5,000+ lbs in OD anyway. MANY aftermarket and even GM grind cams come on stronger than the stock cam, well below the RPM that you would be running while towing in 3rd gear. 5.7 Vortec can sing 3,000 rpm @ 70 pulling 5,000+ lbs all day long. Get into the mountains pulling a heavy load and you are going to be screaming 4,000+ rpm in 2nd anyway. With an automatic transmission you want a cam that makes power from 1,800-5,400 for a Vortec truck.


That makes a lot of sense, thanks!


As far as making towing power on this Vortec, I'm not willing to spend much money. Can the LT4 cam be used with stock heads without doing any machining or anything? I ask because I've read about having to machine the spring seats for high-lift cams. I planned to do the 0411 ECU swap and tune it with HPTuners, so that won't cost much, and if the cam is cheap and is a drop-in, then cool. Anything more than maybe $500 or so plus a couple repairs I might need to do - I'll just drive it and start collecting parts for a 6.0 swap.

[kendogg]

Sorry to threadjack, but what does anybody think about instead of cam swapping, just uing 1.6 or 1.7 ratio rockers instead? 1.7's would be right at the limit of what Vortec heads could handle for lift without machining.....

[Fast305]

Sorry to threadjack, but what does anybody think about instead of cam swapping, just uing 1.6 or 1.7 ratio rockers instead? 1.7's would be right at the limit of what Vortec heads could handle for lift without machining.....

I am about to post alot of my old information that I recently found in a folder in a box after I moved, lots of dyno charts and hand notes from my TBI build back in 2006 ish.

What I can tell you is that with Dough Thorley Long tubes, Edelbrock Performer TBI intake, 2 1/2" exhaust my old TBI 350 responded like crazy to 1.6:1 full roller rockers and a good tune. Something to the effect of 30 RWHP and 70 RWTQ!

I am working on a post that will be in the TBI area to tell all.

[kendogg]

I am about to post alot of my old information that I recently found in a folder in a box after I moved, lots of dyno charts and hand notes from my TBI build back in 2006 ish.

What I can tell you is that with Dough Thorley Long tubes, Edelbrock Performer TBI intake, 2 1/2" exhaust my old TBI 350 responded like crazy to 1.6:1 full roller rockers and a good tune. Something to the effect of 30 RWHP and 70 RWTQ!

I am working on a post that will be in the TBI area to tell all.



Thats awesome, thanks so much! Think the 1.7's would be even more of an improvement?

[Doober]

A downside to higher ratios is for proper sweep across the valve stem tip, different length pushrods are needed. This means elongating the pushrod hole in the head.