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Pathetic Towing performance...

I would lean towards the hx35 14cm, hx40 hybrid like sctrailrider had in his old ride. I have an hx40 16cm housing that does well, but I think the hybrid would be ideal for faster spool up to help with low and mid range rpm's when towing.
 
restoguy said:
On the upside, I thought the engine braking feature Bill puts in his tunes worked pretty well. Better than I expected for just keeping the TCC locked up on de-cel. I just want it to stay locked longer, like down to 25-30mph instead of 42.
Click to expand...

The ATT would require the least amount of time to install. The kit should have everything you need to drop it on. Tune from someone else aside of Heath who doesn't like the ATT. BTW locking the TCC to grade brake exposes the weak link in the 4L80E and that is 2 small clutches that only see power when grade braking. I burned the ones in mine up early by grade braking with the TCC locked: and then the TCC clutch in under 50K by locking it in all the time at WOT. 3 gear let off the throttle and the engine drops to idle when the weak clutches have burned off. Been there done that got the t-shirt and it says locking the TCC for braking is a bad idea! The input shaft is also weak and one reason given for unlock TCC on throttle lift. (I am lucky not to have snapped mine off yet.)

I would like the TCC to lock at 35 MPH as well. IMO the factory TC clutch slips too much at 35 MPH and in my testing wouldn't stay locked due to slip with any slight grade/load. ECM unlocks the TCC due to slip with a custom tune. The Yank I have now does stay locked at 35 MPH.

Smoke. Lets set your expectations where they need to be. I suggest you buy a newer DPF equipped diesel. Seriously if you don't want to see smoke period a high RPM turbo is the LAST thing you want to F with on an antique smoky IDI diesel. (Not talking about intentionally rolling coal.) Next you have to wrap your head around a bigger turbo smoking some and being gutless below 2000 RPM. Careful tuning and fuel control can do a lot to reduce smoke under 2K RPM. Yes, Shift early and rev up the "high speed diesel". Stop light to stoplight unloaded will be won by the small turbo. But I will suck your doors off doing 55 MPH or better while you are doing 43 MPH on a extended grade towing/loaded with the large turbo I am running. This is the trade off you are making for high RPM towing power and better MPG towing. Wound up in the upper RPM the smoke can be gone or a light haze.

Again larger turbo moves the power band up in RPM and you need to be mentally prepared to rev it up and use the RPM all the way to redline including extended wound out high RPM pulls. Some people are terrified to rev the engine up and others want to lug the hell out of their 6.5.

GM put the small turbo on the 6.5 to stop the damn smoke the 6.2 and older 5.7 was known for. The trade off is gas engine MPG gutless towing.

You can overcome some of the lost low RPM performance by using a spool valve or higher stall converter. IMO the Stall converter is slightly better than the spool valve as I am in the full power RPM from a dig vs getting there with a spool valve. My 1993 with the ATT and 2400 RPM stall converter is the truck GM should have made. It is as peppy as a GM3 with the fuel turned up unloaded and that's with a small 6.2 NA pump. (vs. a turned up 6.5 turbo pump on a GM3 turbo I recall first hot rodding.) One just has to get used to 2200 RPM at 35 MPH.
 
Last edited:
DieselMike1 said:
I would lean towards the hx35 14cm, hx40 hybrid like sctrailrider had in his old ride. I have an hx40 16cm housing that does well, but I think the hybrid would be ideal for faster spool up to help with low and mid range rpm's when towing.
Click to expand...
There is no low RPM towing. It's called LUGGING! Cooling fan isn't turning fast enough, water pump, same issue, oil pump and oil movement... Parts exposed to high temps for longer amounts of time. Worse the automatic transmission will not let you tow at low RPM as any throttle will shift it to higher RPM.

From a stoplight with a trailer is where smaller turbo's may help. But you are trading top end power that a larger turbo has for that. Both the HX40II I tried and the ATT both needed 2K RPM to light off from a dig. In trade I gave up some top end power with the midsize turbo. On the dyno peak power was the same just higher boost on the HX40II over the ATT.

Always fun to see other turbo experiments but it comes down to "pick your RPM power sweet spot" with turbo size.
 
ne
WarWagon said:
There is no low RPM towing. It's called LUGGING! Cooling fan isn't turning fast enough, water pump, same issue, oil pump and oil movement... Parts exposed to high temps for longer amounts of time. Worse the automatic transmission will not let you tow at low RPM as any throttle will shift it to higher RPM.

From a stoplight with a trailer is where smaller turbo's may help. But you are trading top end power that a larger turbo has for that. Both the HX40II I tried and the ATT both needed 2K RPM to light off from a dig. In trade I gave up some top end power with the midsize turbo. On the dyno peak power was the same just higher boost on the HX40II over the ATT.

Always fun to see other turbo experiments but it comes down to "pick your RPM power sweet spot" with turbo size.
Click to expand...
That's the beauty of a well built holsett hybrid turbo with a large choice of wheels to choose from. Build one for your needs. I don't want to get in the turbo wars here, but there are choices out there that can suit your needs.
 
I don't mind a little haze on tip in or some light smoke at full power, but the buck-tooth hillbillys who engulf 4 lanes with wasted diesel every time they touch the throttle is what makes people drive a prius. They think it makes them look 'cool', but really they just look like pixar's Mater trying to do algebra. I'm not going to scrub an inch of soot off my trailer every time I pull it. If it smokes, it's broke. Period.

I've had this pickup for 40K miles. I pulled a trailer for 1K. Granted I would have used it a few other times if it was working, so call it 2K miles with a trailer. I should err on the side of too small and have better unloaded performance but I think there is room for improvement just the same. Since I have the ATT already, I'll put it on and see. It only costs me the coupler because I got it used and didn't get all the parts. Not sure if I want to invest in a tune for it just yet or not.
 
Playing the Holset parts change-o game can be expensive! But it might be the best way to find the right combo of parts. A VGT controller might be cheaper...
 
Very interesting about the 4L80E problems. I hadn't heard about this before. Are there any fixes for the clutch issue? I'm sure there are better input shafts. That trans has a good rep, at least as a TH400.
 
restoguy said:
Playing the Holset parts change-o game can be expensive! But it might be the best way to find the right combo of parts. A VGT controller might be cheaper...
Click to expand...
You don't have to play the change o game, talk to someone that builds these for a 6.5 tell them what your trying to accomplish and then build the turbo. When I get ready to build my hybrid I will have John at unique diesel do mine. I have done a lot of research on the hybrids and have my housing's and wheels all picked out for the best performance of what I want my truck to do, and that is too tow heavy.
 
I didn't know there were guys who built them. I'm also a cheap ebay whore, so I'm always trying to get a $10 item for $1... Do guys like that let you swap a housing or a wheel to get it just right? Or are you buying new stuff for that kind of testing?
 
I am running that turbo now and love it. But you have to play with the waste gate to get her where you want. Much (way! Miles better!) better top end and it still spools just as fast as a gmx turbo. I am very happy with mine. And if you can weld a downpipe you are in business.
 
WarWagon said:
The ATT would require the least amount of time to install. The kit should have everything you need to drop it on. Tune from someone else aside of Heath who doesn't like the ATT. BTW locking the TCC to grade brake exposes the weak link in the 4L80E and that is 2 small clutches that only see power when grade braking. I burned the ones in mine up early by grade braking with the TCC locked: and then the TCC clutch in under 50K by locking it in all the time at WOT. 3 gear let off the throttle and the engine drops to idle when the weak clutches have burned off. Been there done that got the t-shirt and it says locking the TCC for braking is a bad idea! The input shaft is also weak and one reason given for unlock TCC on throttle lift. (I am lucky not to have snapped mine off yet.)

I would like the TCC to lock at 35 MPH as well. IMO the factory TC clutch slips too much at 35 MPH and in my testing wouldn't stay locked due to slip with any slight grade/load. ECM unlocks the TCC due to slip with a custom tune. The Yank I have now does stay locked at 35 MPH.

Smoke. Lets set your expectations where they need to be. I suggest you buy a newer DPF equipped diesel. Seriously if you don't want to see smoke period a high RPM turbo is the LAST thing you want to F with on an antique smoky IDI diesel. (Not talking about intentionally rolling coal.) Next you have to wrap your head around a bigger turbo smoking some and being gutless below 2000 RPM. Careful tuning and fuel control can do a lot to reduce smoke under 2K RPM. Yes, Shift early and rev up the "high speed diesel". Stop light to stoplight unloaded will be won by the small turbo. But I will suck your doors off doing 55 MPH or better while you are doing 43 MPH on a extended grade towing/loaded with the large turbo I am running. This is the trade off you are making for high RPM towing power and better MPG towing. Wound up in the upper RPM the smoke can be gone or a light haze.

Again larger turbo moves the power band up in RPM and you need to be mentally prepared to rev it up and use the RPM all the way to redline including extended wound out high RPM pulls. Some people are terrified to rev the engine up and others want to lug the hell out of their 6.5.

GM put the small turbo on the 6.5 to stop the damn smoke the 6.2 and older 5.7 was known for. The trade off is gas engine MPG gutless towing.

You can overcome some of the lost low RPM performance by using a spool valve or higher stall converter. IMO the Stall converter is slightly better than the spool valve as I am in the full power RPM from a dig vs getting there with a spool valve. My 1993 with the ATT and 2400 RPM stall converter is the truck GM should have made. It is as peppy as a GM3 with the fuel turned up unloaded and that's with a small 6.2 NA pump. (vs. a turned up 6.5 turbo pump on a GM3 turbo I recall first hot rodding.) One just has to get used to 2200 RPM at 35 MPH.
Click to expand...

I wanted to make some changes to grade braking and even an exhaust brake but after talking to Bill Heath I decided not to. After changing out gearsets and installing larger diameter tires stopping became more a task then I adjusted the ABS controller for tire to brake calibration and have good brakes again.
 
restoguy said:
Very interesting about the 4L80E problems. I hadn't heard about this before. Are there any fixes for the clutch issue? I'm sure there are better input shafts. That trans has a good rep, at least as a TH400.
Click to expand...


Yes, there is a cure for all of the 4L80E's weaknesses. It is called a NV4500 :happy: One limitation that I have yet to figure a way around is the ECM unlocking the TCC on brake application; GM apparently baked this into the code and it is there to stay :dead:

When you switch turbos, get a new tune otherwise the system will just not have complete balance. If using the ATT, Heath has updates for the ATT but last I checked his data was based on theory and customer requests. Consider using KOJO (Leroy can hook you up) for an ATT tune as his curves were from real-world data and customer requests.
 
I spent big on my last 4L80e rebuild got all the latest cryo treated whatever ceramic were I could an kevlar too and some billet here and there then AMSOIL synthetic fluid and triple coolers.

JayThe CPA, I can't agree more with that 4L80e fix.
 
FellowTraveler said:
I wanted to make some changes to grade braking and even an exhaust brake but after talking to Bill Heath I decided not to. After changing out gearsets and installing larger diameter tires stopping became more a task then I adjusted the ABS controller for tire to brake calibration and have good brakes again.
Click to expand...

how did you adjust your ABS controller?
 
JayTheCPA said:
Yes, there is a cure for all of the 4L80E's weaknesses. It is called a NV4500 :happy: One limitation that I have yet to figure a way around is the ECM unlocking the TCC on brake application; GM apparently baked this into the code and it is there to stay :dead:
Click to expand...

The NV is a great transmission with just one flaw. It won't shift itself! I grew up on a farm where everything had a manual trans. I have a CDL and plenty of miles with my hand on a shifter. When I find the right Saturn Sky Redline, it will have a 5spd. That said, if this pickup had a manual in it I would have never bought it! Just my preference.

I talked to Bill about the TCC unlock-on-brake because I wanted it like my bro's Dmax and he said it couldn't be done. GM really made it hard for us on this one. If only we could run a 6.5 on an 0411...
 
restoguy said:
If only we could run a 6.5 on an 0411...
Click to expand...

Yup, and sadly another dead path . . . The killer on that one is that is specific to a gasser.

Even started to look into the 00 - 03 DMax ECM's. So far it is no-go there either due to the differences from IDI to DI.

I do know one member who might hold enough of the keys of knowledge to help take the next leap in ECM knowledge, but just cannot get him to chat with me . . . Oh well.
 
Burning oil said:
You have turbo to fix your problem (ATT) slap it on there! Will take 3 hour max. A tune will get the most from it, but just the turbo alone would have raised your MPGs, lowered EGTs and ECTs
Better fuel delivery will help too.
Click to expand...
:yawn:
 
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