Engine/Transmission (1994 - 1998) Difference between PDR HX-35 and HX-40

[Bob V]

I would like to know what the people that have ran both the PDR HX-35 and the HX-40 think. What is the difference in low and mid range power? How much of a EGT reduction? has anyone towed with both? I would like to go with the HX-40 but the cost of it and a new exhaust brake is just too much. I am also looking at the HTT stage three kit. Anyone knows how this compares to the PDR HX-35?

BTW my truck is a '97 5spd, #10 plate, 3000 GSK, 370 injectors, running the stock turbo with the 16 housing.

TIA

Bob Verhoef

 

[Deezul1]

Cant tell ya much about the HX40 but I just installed a PDR 35 w/16 housing and am extremely happy with it. I really need a 40 at my power level but like you don't want to go to the bigger exhaust and another E brake plus turbo expense. The PDR 35 spools quicker, makes less smoke, EGTs rise slower to the point I don't have to watch it unless I am racing , and generally is more responsive.

 

[kentdiesel]

Bob V

IMO, with the fuel level your at the PDR-40 is definetly the direction to go. I know it costs more but the extra air will be better for your engine. I have towed 17,500 lbs gross with a PDR-40 and lag is not a problem and neither was EGT's. Piers told me that it would take a PDR-40 to keep EGT's under control with a #10 plate in my truck and he was right. I have stock injectors and I would not want any smaller turbo. If you have not advanced your timing that would be something to consider as it will lower EGT's. I'm curious, with the stock turbo what is the highest EGT your truck has went to?

Kent

 

[dpuckett]

I got my PDR 35 from a guy who put a #10 in his 96, ended up having to go to a PDR 40 anyway; EGTs too high under a hard pull. Save yourself the time and effort, even if it means a few (hundred) extra dollars upfront. Or you might look into a HX35/40 hybrid that some vendors are advertising.



Daniel

 

[Rams-n-Hogs]

Bob,



I'm running HTT's stage 2 compressor housing, for the very reason you mention. I wasn't ready for the expense of the HX-40 and a new exhaust brake. It makes a 100-200* drop in EGT's over the stock turbo with a 16cm housing. My spool-up is back to what it was with the 12cm housing. I can't compare it to Piers turbo's because I haven't run either one of them. You can still get hot if you push it, but it's controllable with the right foot, easier than the stock turbo is. Just changing the housing and wheel, I gained 30+hp and 120ft/lbs, and my smoke level went down quite a bit. I still want to go to a bigger charger, eventually, but in the interim, this works for me. Haven't done any real towing with it, yet. I was pretty impressed with it when I installed it.



Jim

 

[BushWakr - RIP]

Not being a true "expert" on turbo's but here is my take (personal opinion)

The PDR HX35 is an extremely good turbo; it is tuff, responds extremely well even with moderate fueling and has a nice upper end map compared to any of the stock turbos in this range.

The boost is certainly cooler even at the upper ends...

There is an area of "overlap" that comes into play when you bring the HX40 into this... as the HX35 (hybrid) starts to run out of it's map and get hot the '40 steps in and takes over.

From there the 40 is all over the 35.

At my current fueling level in my 1st Gen, I am in need of an HX40 BADLY!! If I get a bit crazy I can hit 1600*F or more on a long hard run... .

Since the 1st Gens do not normally run the kind of fueling/HP/torque of the 2nd Gens it stands to reason that the '40 would work well for you.



Hope that helps in your decision... .



Pastor Bob ~ PDR - BLack SHeep RAcing

 

[mstimac]

I'm currently Running a 98' 12V with the 180 pump, 370's and a 6 plate. Am I out of the map for a PDR 35?

 

[vssman]

Bob,



I have the stage 3 hybrid (12cm exhaust) and it's great! No lag at all. I did that instead of a 40 for the same reasons mentioned above. Also, the 'cost' of the kit is relatively small compared to a new turbo - mine was $210. 00 shipping included v. s. $1200. 00 plus a down pipe and shipping. If I don't like it, I can always try to sell the hybrid and go with something else. Hmmm, I wonder if the hybrid is a good turbo for a set of twins...

 

[BushWakr - RIP]

An HX35 can be pushed to roughly 35-38psi and still run fairly well.

At 40 psi boost an HX35/12 will be seeing rougly 72psi drive pressure. That is too high and is certainly causing high boost air temps as well as EGT rise, with those two factors feeding off one another... .



For comparison sake the same turbo above but using a 16cm housing will have approx. 45psi drive pressure at the exhaust housing inlet,... better but still high (40psi boost/45psi drive).



An HX40/16 with 46psi boost (sorry haven't done a comparison at 40psi boost) will show approx. 40psi drive pressure ... so now you have 46psi boost/40psi drive press.



Our HX 40's are 'gated at 38-40psi. That keeps the pressures in check the EGT's reasonable (usable) and helps hold off compressor stall or shaft issues.



mstimac... . Depending on your plate setting and whether you have the stock exhaust housing on the turbo you will be pushing the '35 up there in terms of 'map'.

You'll want to do some "matching" on your setup. Your fuel plate/its position/truck load/boost pressures etc should be tailored to suite your driving. Do you tow heavy, do you just rat race around in town etc etc... .

On my truck right now, I can bang up to 43-44 psi almost instantly, but I am well into the "not good" range for the 35/16 I'm running.

I could either go with an 18. 5cm housing or step up to the HX40/16, with the latter being more effective for my use.



Bob.



Bob.

 

[Bob V]

I did some work on my stock 12 to get the waste gate to fully open with a small difference in pressure between start to open and fully open. Comparing the drive pressures on my truck, with the modified 12 , my max drive pressure is 47psig, max boost, 40psig. . With the 16, max drive was 60 psig and max boost was 45 psig. I think that I got lucky and have a good flowing stock housing. I think that I will be going with the modified 35 for now. I just don't have $2000 for a 40 and e-brake, and I don't want to go without a e brake. If I am not happy with the 35 I wont be out a lot of money and I will have a better set up than I have now while I save for a 40