Hey, recently I swapped out an HX35 turbo for an HX40/35 hybrid. Used the 14cm2 exhaust housing. Wanted to check the results out against what other people here might know.

Power's up, the truck can really scoot uphill now. A bit more smoke, too. But the EGT thing is what I didn't expect. The pyro gauge has really gone ballistic, the EGT's rise like a rocket, peak on the hills in 6th gear (unloaded) at about 1100*F, and then fall like a stone back down to 500-600*F. Cruising at 70 mph, they're about 750-800*F. So the EGT's rise faster and farther and fall faster and farther than the old HX35/12 cm2, but stay about the same at cruising. Didn't quite expect this.

Oh, and I got an Edge Comp, pump wire not hooked up, 275 injectors, and usual mods to exhaust & intake.

Appreciate any comments on whether this is usual. Thanks.

 

Please include your signature showing vital stats on your truck. Assuming ETH/DEE, as you mentioned 6th gear.

This does not make sense to me. More air is supposed to equate to cooler EGT's? Assuming that all is well with the snail, have you checked for boost leaks?

What happened to your boost pressures?

I assume that you are running a pre-turbo probe?

With just the 275's, I had EGT issues towing. With the addition of the untapped comp, the extra boost more than made up for the increased fueling, and EGT's were not a problem. Especially unloaded. No issues there at all.

Seems a bit odd to me, am I missing something?

 

Sorry -- 2002 ETH/DEE 3500 4x4, Edge Comp, 275's, AFE cone on the intake, 4 inch exhaust, boost/fp/pyro gauges.

Pyro is pre-turbo, back three cylinders on the exhaust. Boost goes up to at least 35, pyro gauge doesn't go beyond that, but I haven't cranked it up because I'm still babying the turbo bearing. Had it at 30 psi on a 8% interstate grade at 3000 feet for several miles, hit 1125*F unloaded. But just backing off slightly caused the pyro to plunge 200*F. Down the mountain, the EGT's go real low real fast, below 400*F, never seen that before. Tried the turbo with a 12cm2 exhaust housing, and the EGT's were about 150*F higher than the HX35. With the 14cm2 housing they're about the same highs as the 12cm2, but lower lows, and the pyro really rockets back and forth. Also noticed that the fuel pressure gauge shows about 1-2 psi less -- so I'm burning more fuel. And yet, fuel mileage is up about 2.2 mpg after a 400 mile trip.

Any of this make sense?

 

Sadly enough, I have not yet gotten to that point of mods where I need a bigger turbo, but I would expect the same results you have described. I may just be shooting in the dark here assuming that your EGT's are shooting up faster due to the extra lag time of the bigger turbo. And since you have yet to tap the wire, by not adding more fuel, that lag time is exaggerated. Your stock HX35 was spooling by the time the EGT's where comming on so thats why you didnt see your temps shoot up like that. And since the new hybrid unit comes on later and pushes more air you should see the EGT's jump up untill boost comes on then drop to a much lower temp. Cruising EGT's should be about the same since you arent adding more fuel than before with the stock HX35. I would think the biggest difference you'll see is pulling a trailer. Thats where the extra air will keep those EGT's down. Just curious but why get a hybrid unit and not tap the wire? Well anyway like I said I'm not sure due to lack of experience with changing turbos so it will be funny to see if I was way off base on my cunclusion. Hope I didnt make things worse for ya.

 

I didn't tap the wire because I got no reason to deal with the consequences of stressing the VP44. I don't race, I tow and do highway miles in the mountains. I got the hybrid turbo because the HX35 was going bad, had too much play in the shaft, and I figured, why buy another, take a step up. I like the way it runs a lot, and there's not much more lag than there was with the stock unit. But I did expect the EGT's to go down more than they have. I don't see the big drop in EGT's when the boost comes in, and I'm wondering what's going to happen when I start towing next spring and summer.

 

I do not have this combo but it makes since to me. I think KATOOM hit the nail on the head with his comments. I think if you had the wire tapped or larger injectors you would ahve noticed more of a change, because your EGTs with the 35 would have been higher to begin with. You would be amazed towing with the wire tapped. I ran a comp with wire tapped, 275s and an HX35 for a while towing about 12K. It was a little smokey but i didn't traffic up with slow take offs.