• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

HX40II Turbo Install

The difference between the GM turbo and any HX40 or ATT is that the fueling will more appropriately control how much boost you get, and not the PCM. The GM turbo is so small it has to have the wastegate controlled a lot, and not so on a larger turbo. EGTs and a safety net is all about fueling level. If you want that safety then youre looking for stock fueling levels and about 12psi of boost, but you wont like towing 10k lbs like that. The 6.5 and HX40/ATT are capable of a lot more safely.

I would be looking for a typical performance level program, that maxes out the GM fueling curve at 80mm^3 at 2100psi to 3300rpm, but no more fueling tweaks. And no extreme advance, but more than stock under load because it will help lower EGTs with more fueling. Get a controller that pops the wastegate of the HX40 around 15psi of boost. That and a good set of injectors will get you far (which I recommend set to pop at 2300psi). Assuming you already have a 4" exhaust and a decent cold air intake.

You foot becomes the factor in how much fuel and boost you get, but you should not have any issues with a setup like that. Sometimes it becomes dangerous not having the capacity for more power, because at times going too slow is both frustrating and harder on the engine not having any air flow, so the fan must take more power from it. That and all the little racers on the highway flying past you.
 
Good post as always. Thanks. The TM style waste gate controller or the one an HX would come with don't compensate for altitude. On the trip home from Texas I couldn't wait to get back in the Willamette Valley and denser air. Passing 2 semis at high altitude on a two lane road takes planning and patience. You or GW mentioned a blank table that looked like GM was going to set up for altitude compensation.
Any dyno data on this mod yet?
 
Hopefully I can get Jamin6.5 on the dyno on the 30th of this month. I might even get our club to pay for it if I can. Of course, just to see.
 
Gm did set up for altitude compensation, used it in "S" L56 truck, just ignored it in "F" L65 trucks. I have climbed the Rockies with no wastegate at all and can tell you, that you dont need the compensation when you have the fueling and power to climb the grades. It becomes a non issue when your truck just kicks ass compared to the POS stock setup. Now the compensation is good for around town driving when a mile high. To try to prevent some smoke screens off the line, but is not needed at highway speeds where the turbo is already spooled.
 
How many lbs/min does the 6.5 need? It seems unbelievable that GM would put such an anemic stock turbo on our trucks.
 
skypilotj said:
How many lbs/min does the 6.5 need? It seems unbelievable that GM would put such an anemic stock turbo on our trucks.
Click to expand...

That all depends on what air to fuel ratio you want and how much fueling you have.

In stock form, the GM turbo may be able to flow an adequate amount of air mass, but that doesnt mean its an appropriate choice.

at max 65mm^3 fueling at 3000rpm and 18:1 air to fuel ratio you only need about 25lbs/min

but at 80mm^3 and 3500rpm at 18:1 air ratio you would need about 37lbs/min

For those with a good performance setup, 96mm^3, 3900rpm, 18:1 air ratio would need about 49lbs/min

Those with the real high performance rigs, 110mm^3 out to 4500rpm and 18:1 air ratio would need 65lbs/min

Increase the fuel rate, RPM or your desired air to fuel ratio and you need more air mass per minute.

6.5L at 3500rpm ~ 400CFM, at 15psi of boost you would need twice as much air through the turbo, so about 800CFM through the turbo for 400CFM at twice atmospheric pressure. At 200F IAT that would be 48lbs/min, but sustained the GM turbo is likely to be more like 300F IAT, which would be 42lbs/min, and since the engine isnt perfect, we could assume it flows 90% of that, which would be almost 38lbs/min. It heats up the air because its inefficient in that pressure range and restricts the exhaust a lot. The resitriction also robs horsepower.

You could put an intercooler on with the GM turbo, to compensate for its inefficiency, but can it really support more mass flow? To spool it even more would just make more backpressure, more restriction.

6.2Turbo's modified DB2 was putting out 110mm^3 at high rpm, more at low rpm. And although some have claimed their DS4 programs could put out up to 96mm^3 I have seen no evidence that was true, other than I know it can be done and have done it. I have seen programs and they werent anything special over the max 80mm^3 in the fuel table, and they werent able to drive the ATT to any more boost than 80mm^3 has shown will do. But you can drive the ATT over 20psi of boost with a DS4. The HX40WII is much easier to get to 20psi boost, since its a little smaller. The HX40 compressor map fits quite well with a decent 6.5 performance setup and the HX40WII provides quick spooling. It is a good match, more so than smaller turbos, but the real high performance guys would likely use a larger HX40 or ATT. Or even an HX52 in 6.2Turbos case with the small 16cm^2 turbine housing. The larger the turbo, the less you really have to be concerned about controlling it, as fueling and flow will dictate how much you can spool it, and not how you control the wastegate.
 
Holy Monkeys! Thats some good info. I know enuff now to get my self in trouble 4 sure. Thanks. From looking at the HX40 compressor map it looks like a 6 blade wheel would be the way to go with a mild tune. Whats in the way of a 4" down pipe on our trucks?
 
skypilotj said:
Whats in the way of a 4" down pipe on our trucks?
Click to expand...

Have you looked back/down there. The HX40WII only has a 2.5" ID outlet, so no need being reason one. The turbo sits so far back that even a 3" elbow is hard to fit on it without hitting the AC dryer. A non wastegate turbo gives more room in this respect, not sticking so far out of its housing. Then the frame to cab or engine/exhaust crossover clearance can be difficult even with a 3" pipe. With a lift kit there is more room, and 4" has been done before, but I dont see it as necessary, especially not with the HX40WII or anything smaller.
 
I see now. When you say lifted you mean body lift or suspesion?
As for the The HX40WII with the six blade compressor wheel?
 
I'm sure he meant body lift as a suspension lift wont affect the clearance between the manifold, body, fender and frame at all.
 
Thats what I thot. Just wanted to be clear. I have a 6 inch lift and a poorly fabbed crossover from the PO. Its on my list for the next round of upgrades in July.
 
jhornsby3 said:
Hopefully I can get Jamin6.5 on the dyno on the 30th of this month. I might even get our club to pay for it if I can. Of course, just to see.
Click to expand...

I am still planing on comming. I just got the turbo on today And first results are good. Trans is not happy. It might need a rebuild on the trans. Pulls hard till the trans slips. Plus the new turbo sound great!:
 
Jamin6.5 said:
I am still planing on comming. I just got the turbo on today And first results are good. Trans is not happy. It might need a rebuild on the trans. Pulls hard till the trans slips. Plus the new turbo sound great!:
Click to expand...


I blew my tranny second day after i installed my hx40II turbo, be carefull!!
 
Its better to run an aftermarket PCM program, because they should up the transmission pressure hopefully. So that it will handle power better. There is a lot of room to increase the tranny line pressure in the PCM programs.

Jorge, if your truck is not shifting right, the rebuild could have put the wrong Pressure Control Solenoid (force motor). There is one for 93 and earlier, and one for 94 and later, using differnt PWM frequencies. Might have used a rebuild kit for an older 4L80E. Do you have another thread for your truck?
 
Hey buddy thanks for the input. I do have a thread about my tranny issues in the gm transmission 4l80e section. check it out.
 
So i have installed the HX40 and the truck drive great unloaded. but if i try and tow it defuels. Any suggestions? I know that a new ecm will fix it but don't have the funds right now and am looking for a different option for the short term.
 
Why is it defueling? sustained overboost? Could do a boost fooler. Not an ideal fix, but it works. 10k resistor in the center wire of the MAP harness. computer sees ~2.5psi lower than is actually going on.

Or adjust whatever boost control you're using to lower levels.
 
You must log in or register to reply here.
Back
Top