2003 Sierra sycloned
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On The Tree
Joined: Oct 2018
Posts: 146
Likes: 15
From: Sioux Falls, SD
I’d probably be happy with high 11’s.
Yes the 60 is bad but it doesn’t spin at all even with this smaller turbo. Tires are regular 31” takeoff radials. Footbraking it gets to about 0. How long are most waiting to build boost?
I realize it’s a lot easier to make a straight up race car but I am trying to make a street driven truck slightly better.
Yes the 60 is bad but it doesn’t spin at all even with this smaller turbo. Tires are regular 31” takeoff radials. Footbraking it gets to about 0. How long are most waiting to build boost?
I realize it’s a lot easier to make a straight up race car but I am trying to make a street driven truck slightly better.
I’d probably be happy with high 11’s.
Yes the 60 is bad but it doesn’t spin at all even with this smaller turbo. Tires are regular 31” takeoff radials. Footbraking it gets to about 0. How long are most waiting to build boost?
I realize it’s a lot easier to make a straight up race car but I am trying to make a street driven truck slightly better.
Yes the 60 is bad but it doesn’t spin at all even with this smaller turbo. Tires are regular 31” takeoff radials. Footbraking it gets to about 0. How long are most waiting to build boost?
I realize it’s a lot easier to make a straight up race car but I am trying to make a street driven truck slightly better.
You need it to build boost foot braking. If you can't, it will never 60'. It is possible to foot brake zero ish psi... and when you let off the foot brake boost will hit instantly. But again, you need a looser converter to do anything really.
How much rpm can you foot brake before spinning the wheels? Have you looked into the "sloppy trans brake" mod they do to the 4l80 4l60e's? Might look into that and/or really beef up your rear brakes. could even add another caliper to help hold the wheel from spinning. There are other small tricks. Like extending your brake pedal for more leverage so you can really press hard on that brake pedal. Adding an electric vac pump to the brake assist etc etc...
I think you could hit your goal with 600 hp or so. A smaller turbo is also an option. One that would spool more quickly. the 78/75 isn't the best design for a quick spooling turbo. Generally, you never want the compressor larger than the exh wheel.
You could also smack it with a 50 shot of nitrous for 1-2 seconds off the line to get it going.
Bottom line, you need to build boost from a stop if you ever want it to perform. The best way by far is to put the correct converter in the car.
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FWIW , I'm at 4420 lbs running a best 60' of 1.65 . Can't leave on boost as not enough traction, have to foot brake to 2500 in vacuum or boost comes too quickly and blows the tires off . Ptc converter can be stalled on the DRs to about 3000 but it doesn't help . 6L 7875 4l80e combo, 3.73s 30 " tires
Heavy weight and loose converters make for not so fun response at anything other than WOT. A 2 step can more than make up for launching in boost and still not require a loose converter.
Its a 4.8 in a heavy vehicle. There's only so much you can do. If you want it to make boost off the line and 60' decently... it needs a converter. (or 150 shot! lol) Not a lot of options. But I guess we'd have to define a "loose converter" Because the "3000 stall" Circle D converters I worked with would flash to like 2400ish behind a 4.8. That's WOT flash form a stop. They are the extreme opposite of a loose converter IMO.
The converter I have now was said to be super loose. Almost the loosest converter PTC makes w a 20-5 stator. WOT flash on my 5.3 and I see 3500ish. Would see less with a 4.8. Now once boost starts to build, the stall rpm along with the boost will go through the roof if I let it. But I still think any turbo car needs to build boost from a stop in someway... if he wants it to run a decent ET.
Last edited by Forcefed86; Sep 25, 2023 at 01:41 PM.
According to whom and what converter? I guess I haven't driven any heavy weight race cars. But I use to have similar issues in the grand national days. Loose converters did as you say... But that all changed when converter tech changed IMO.
Its a 4.8 in a heavy vehicle. There's only so much you can do. If you want it to make boost off the line and 60' decently... it needs a converter. (or 150 shot! lol) Not a lot of options. But I guess we'd have to define a "loose converter" Because the "3000 stall" Circle D converters I worked with would flash to like 2400ish behind a 4.8. That's WOT flash form a stop. They are the extreme opposite of a loose converter IMO.
The converter I have now was said to be super loose. Almost the loosest converter PTC makes w a 20-5 stator. WOT flash on my 5.3 and I see 3500ish. Would see less with a 4.8. Now once boost starts to build, the stall rpm along with the boost will go through the roof if I let it. But I still think any turbo car needs to build boost from a stop in someway... if he wants it to run a decent ET.
Its a 4.8 in a heavy vehicle. There's only so much you can do. If you want it to make boost off the line and 60' decently... it needs a converter. (or 150 shot! lol) Not a lot of options. But I guess we'd have to define a "loose converter" Because the "3000 stall" Circle D converters I worked with would flash to like 2400ish behind a 4.8. That's WOT flash form a stop. They are the extreme opposite of a loose converter IMO.
The converter I have now was said to be super loose. Almost the loosest converter PTC makes w a 20-5 stator. WOT flash on my 5.3 and I see 3500ish. Would see less with a 4.8. Now once boost starts to build, the stall rpm along with the boost will go through the roof if I let it. But I still think any turbo car needs to build boost from a stop in someway... if he wants it to run a decent ET.
Since every tenth in the 60 is worth two in the quarter. 12.47 @ 113 on the street...you're running as fast as the other guy's high 11's (assuming all the launch mods got you 1.7 or 1.8 sixty).
If this is for the street, is that low 60' you're shooting for going to even apply/help?
For a DD driver truck I'd stall it a little and forget about the other launch stuff, and just bring the power up to the driveline limits and drive it if it were me.
With the extra weight, I think the realized stall is going to be a little higher than a lighter car anyway at WOT I believe since the extra weight raises the push wall. You probably want to aim lower instead of higher on the stall estimate. But yea high stalls are somewhat annoying for DD duty.
I would love to find some cheap easy LS AWD solution, so much room and parts are so plentiful on the trucks.. but they are just so heavy you need like 30% more power to equal an fbody.
Last edited by mk3cn4; Sep 25, 2023 at 03:38 PM.
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Joined: Dec 2004
Posts: 2,177
Likes: 627
From: Florida
silverado is the easiest im aware of.
s10 is super tight and still not very light if you use a 98+
people have done subarus but the motor hangs way out front and i cant imagine anyone would call that swap easy.
some audis?
the scrap yard a bunch of years ago said mine was 4900 with me in it. aluminum block but w/a intercooler and small onboard air setup.
s10 is super tight and still not very light if you use a 98+
people have done subarus but the motor hangs way out front and i cant imagine anyone would call that swap easy.
some audis?
the scrap yard a bunch of years ago said mine was 4900 with me in it. aluminum block but w/a intercooler and small onboard air setup.
Converter tech is certainly better than it used to be. Even the same stall rating from 2 different manufacturers can drive very different from one another. A 3k stall isn't loose if its a quality converter. Many LS guys run converters sized at peak torque, so they're in the 4400-4800 range. I wouldn't want something that high in a heavy truck unless it was a drag setup that was being rev'd to 8k. A 2 step would only help the car build more boost on the line, regardless of choice of converter/stall. I'd rather err on the side of slightly smaller and run a 2 step then get something that is overly loose and doesn't drive as nice on the street.
I do have a personal hatred of circle D, I must admit. They don’t seem built poorly, but I’ve never once seen one of their converters stall where they were meant to. Maybe they are all rated for 4700lb trucks with OEM gearing and they hit the stall perfectly in that situation. I’ve just yet to see on any of the cars I’ve tuned. (which I admit aren’t full sized trucks). To be fair some of that could be on the owners giving Holdner HP numbers to the converter company. But its to the point I tell guys to order 4000 stall and tell them the motor makes 250hp.
Not saying its not cool and unique. Just not practical.
AWD stuff is fun, but it will nickel and dime you to death if you don’t spend a mint on it initially. And even then… parts are gonna break. And for what? A 1.8 60’ on an unprep’d surface?
I ran AWD DSM’s for many years. They are cool for sure! I managed consistent 1.6ish 60’ times and ran the exact same tune and launch RPM on the street. Honestly believe I was around the same 60’ on the street. But the broken axles/cases/trans got old. And I was only 3300lbs and made MUCH less TQ. I actually ran snow tires on mine. They act like cheap drag radials. Gave me just enough slip I didn’t break axles as often, but hooked much better than a standard radial. (cheap too).
There's a local guy here with a 3/4 ton 2000's extra cab chevy truck with a built 6.0L and 7875 turbo who races the truck in 4x4 mode and watching it leave the starting line is always fun.
It hikes the front end up in the air while the front tires are steering around all over the place fighting for traction.
Wanna say he runs high 10's with it and is on his second or third t-case and front diff but he loves it lol.
He catches a lot of would-be fast street cars off guard with it on the street.
It hikes the front end up in the air while the front tires are steering around all over the place fighting for traction.
Wanna say he runs high 10's with it and is on his second or third t-case and front diff but he loves it lol.
He catches a lot of would-be fast street cars off guard with it on the street.
Have to say I’d want the exact opposite. I don’t get how a loose converter would drive worse? It would allow the TQ multiplication to get into boost more quickly from a roll and from a stop. Tight converters on a 4.8 with a big turbo would drive 10x worse IMO. It would just lug until it made boost. Need a little S366 on there or something similar if he wanted 550whp and boost from 2k to 6k. Which isn’t the happy zone on a 4.8 at all.
I do have a personal hatred of circle D, I must admit. They don’t seem built poorly, but I’ve never once seen one of their converters stall where they were meant to. Maybe they are all rated for 4700lb trucks with OEM gearing and they hit the stall perfectly in that situation. I’ve just yet to see on any of the cars I’ve tuned. (which I admit aren’t full sized trucks). To be fair some of that could be on the owners giving Holdner HP numbers to the converter company. But its to the point I tell guys to order 4000 stall and tell them the motor makes 250hp.
I do have a personal hatred of circle D, I must admit. They don’t seem built poorly, but I’ve never once seen one of their converters stall where they were meant to. Maybe they are all rated for 4700lb trucks with OEM gearing and they hit the stall perfectly in that situation. I’ve just yet to see on any of the cars I’ve tuned. (which I admit aren’t full sized trucks). To be fair some of that could be on the owners giving Holdner HP numbers to the converter company. But its to the point I tell guys to order 4000 stall and tell them the motor makes 250hp.
TECH Addict
Joined: Dec 2004
Posts: 2,177
Likes: 627
From: Florida
OEM AWD components aren’t meant to hold any decent amount of power and will break very easily. Esp. @ full sized truck weight w a sticky tire. You could swap to 2WD lose a ton of weight, gain a ton of reliability. Could 60’ better with 2wd and a decent tire/suspension as well IMO.
Not saying its not cool and unique. Just not practical.
AWD stuff is fun, but it will nickel and dime you to death if you don’t spend a mint on it initially. And even then… parts are gonna break. And for what? A 1.8 60’ on an unprep’d surface?
I ran AWD DSM’s for many years. They are cool for sure! I managed consistent 1.6ish 60’ times and ran the exact same tune and launch RPM on the street. Honestly believe I was around the same 60’ on the street. But the broken axles/cases/trans got old. And I was only 3300lbs and made MUCH less TQ. I actually ran snow tires on mine. They act like cheap drag radials. Gave me just enough slip I didn’t break axles as often, but hooked much better than a standard radial. (cheap too).
Not saying its not cool and unique. Just not practical.
AWD stuff is fun, but it will nickel and dime you to death if you don’t spend a mint on it initially. And even then… parts are gonna break. And for what? A 1.8 60’ on an unprep’d surface?
I ran AWD DSM’s for many years. They are cool for sure! I managed consistent 1.6ish 60’ times and ran the exact same tune and launch RPM on the street. Honestly believe I was around the same 60’ on the street. But the broken axles/cases/trans got old. And I was only 3300lbs and made MUCH less TQ. I actually ran snow tires on mine. They act like cheap drag radials. Gave me just enough slip I didn’t break axles as often, but hooked much better than a standard radial. (cheap too).
TECH Addict
Joined: Dec 2004
Posts: 2,177
Likes: 627
From: Florida
It sounds like were talking about 2 different scenarios. You're talking about hitting it on the street at WOT and I'm talking about driving through parking lots and part throttle stuff. That's when big sloppy converters suck. All I was getting at is I would run a tighter stall for better low speed and cruise drivability and let the 2 step do the work of building boost on launch. From a roll won't matter much as the truck will downshift if tuned right and you're in boost instantly anyways.
sounds like you might need to buy more expensive converters. my awd truck will push past 4000 foot braking but drives around parking lots just fine. my wagon will flash to 5000rpm but only has 3-4% slip at 2200rpm cruise without lockup. also does just fine in parking lots. both are FTI converters ranging in original cost from 1300-1900
20 years of people coming on this site with similar experiences would disagree with "just throw money at it. " Obviously some companies are much better than others, but at some point viscous coupling and physics intervein. But I forgot this is the internet and everyone has an unobtainium torque converter and all cams drive like stock.
One car, one combination and a series of converters looking at rated stall vs actual stall, ET and MPH 1/8 and 1/4 mile, coupling capability (shift drop), heat generation, top end slip and dyno pulls for fun.
Give the torque converter companies accurate data and see who does it better.
Sorry, kind of off topic but you know what would be cool, would be a torque converter comparison test.
One car, one combination and a series of converters looking at rated stall vs actual stall, ET and MPH 1/8 and 1/4 mile, coupling capability (shift drop), heat generation, top end slip and dyno pulls for fun.
Give the torque converter companies accurate data and see who does it better.
One car, one combination and a series of converters looking at rated stall vs actual stall, ET and MPH 1/8 and 1/4 mile, coupling capability (shift drop), heat generation, top end slip and dyno pulls for fun.
Give the torque converter companies accurate data and see who does it better.
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Joined: Dec 2004
Posts: 2,177
Likes: 627
From: Florida
as an engineer you should know better than anyone how unfair and disingenuous calling it 'just a viscous coupler' is.
ive had cheap converters ($200), mid level ($1800), and many in between and in my experience the extra spent on a converter has a much larger day-to-day impact on a hot rod than camshafts, turbos, compression ratios, or just about anything else besides tires.
this hobby isnt for everyone though, and some would rather have pretty wheels or fancy paint. thats what makes the hobby interesting.
ive had cheap converters ($200), mid level ($1800), and many in between and in my experience the extra spent on a converter has a much larger day-to-day impact on a hot rod than camshafts, turbos, compression ratios, or just about anything else besides tires.
this hobby isnt for everyone though, and some would rather have pretty wheels or fancy paint. thats what makes the hobby interesting.
TECH Addict
Joined: Dec 2004
Posts: 2,177
Likes: 627
From: Florida
Sorry, kind of off topic but you know what would be cool, would be a torque converter comparison test.
One car, one combination and a series of converters looking at rated stall vs actual stall, ET and MPH 1/8 and 1/4 mile, coupling capability (shift drop), heat generation, top end slip and dyno pulls for fun.
Give the torque converter companies accurate data and see who does it better.
One car, one combination and a series of converters looking at rated stall vs actual stall, ET and MPH 1/8 and 1/4 mile, coupling capability (shift drop), heat generation, top end slip and dyno pulls for fun.
Give the torque converter companies accurate data and see who does it better.
i hate calling companies to waste their time and mine asking questions as much as the rest of us, but converters its gotta be built to your combo or you need a cookie cutter combo and some luck to get something good.