Engine/Transmission (1998.5 - 2002) lot's of turbo questions and will it work with BIG(200hp) injectors

[ScottWright]

I might have an opportunity to put a HX-40 on my truck. It's not a piers one it's just stock. I have some questions about it though. (and please I am just going on the best of my knowledge so feel free to "edge-ah-makate" me!)



I have to believe that the hx-40's that broke in the past were because of overspeeding that big wheel (aka big boost #'s) Has anyone had any problems with a stock HX-40 that kept the boost #'s down (below 40psi or so?) Big wheel can't handle the high inertia from the wheel RPM to create big boost. The HX35 is more forgiving because of the smaller turbine (I think anyway right?)



Also if you are going to keep the boost numbers down, is there any real advantage to it over my hx-35/16cm at 45psi? I know that the HX-35 is inefficient at those boost levels, but you're still moving a bunch of air. They both have the same ex housing size, so will there really be an improvement with the EGT's on the HX-40 (I'm guessing not because with the same size exhaust housing how could it?) I can vaguely read the poor turbo maps from Holset. Seems like the HX-40 can move a bunch more air through the exhaust side then the HX-35 can. Looks like about . 375 vs . 5 kg/s? But that really doesn't mean squat because our 5. 9L would have to run at 6000 RPM @25psi to take advantage of the hx-40's air movement? Mass air flow rate in, is has to equal mass air flow rate out right? (plus some fuel quantity in the air, but does that really effect it much? I calculated that to be only about . 05 kg/s @ 500hp and a . 65 bsfc) So where is the advantage of the HX-40 at? on the cold side? It doesn't really look like at 35psi the HX-35 and HX-40 are too much different in efficiency (but again vague holset mapping info) Can anybody explain this?



As for injectors. I have a set of bd6's, supposedly 200hp (not too much info on them around here though) Has anybody run a real big injector on a hx-40? I have a drag comp and dd3's right now with the hx35/16cm. It was actually stuck on 5 x5 for about 2 months and I didn't have any problems (just needed to learn to use a little finesse on the go peddle that's all. ) I can't believe that a 200hp injector has any more fuel then the drag comp and the dd3's together. Not to mention you could run the drag comp on 1x1 and slow the fuel curve way down. Then just crank it up when you're ready. Any idea how much power this setup would make? I'm thinking maybe 525hp or so? How about adding water/meth to compensate for not enough turbo? Thanks in advance guys, I'm gonna post this one in the COMP forum too.

 

[jaybigboy34]

I run around 145hp injectors and a puck with a 40 turbo and I don't have a bit of problems.

 

[KLockliear]

Just be aware that there are 20 different part numbers of HX-40's in the Holset catalog. The key is to make sure you get the good one, and wastegate it for a max of 40psi.

 

[Hohn]

Some 40s are much more forgiving than others. They aren't all the same.



That said, the HX40 is weak overall. There are ways to make it live, but those mostly involve not using the HP you have.



It's not just overspeeding that kills 40s. It's the transitions from one turbine speed to another-- ACCELERATION. THIS what also kills 40s.



With all respect to Jay Big Boy, a 35/40 hybrid is VERY different than a full 40. One of the main reasons the 35/40 was developed is the tougher turbine section of the 35 (smaller wheel).



With 200hp injectors, you can dump a lot of fuel into the engine in a very short time. That means you could see huge acceleration spikes in the turbo. IOW-- I don't think a full 40 and showerheads is a very good idea.



With that large an injector, I'd recommend something both a little bigger and a little tougher-- a B-series, an HTB2 from Hi Tech Turbo, a '55 variant from J. R. Adkins, etc.



A 40 can live, but I wouldn't trust a stock one. Even modified ones can explode more easily than you think (DD, Piers, etc).



Add 200hp showerheads and all bets are off, imho.



Justin

 

[ScottWright]

Like I said, I don't know a whole buch so I appreciate all the help I can get, and I will learn from anyone. Thanks again everyone for input. . .



Could you answer a few questions for me Hohn?. . . . (or anybody for that matter )



Is it the acceleration of the wheel, or the decel of the wheel that kills it? I know that the big wheel has a bunch of lag so I am assuming that the accel rate on the wheel isn't that high? Now the decel on the shift's I can definataly believe that, but on an automatic is it really that bad? You never let off like a stick (for most who can't really row 'em!) so you don't get that sharp fuel/boost loss.



What fails on these things? If it is truely the shaft breaking without the wheel coming apart, I definately buy the whole accel/decel theory. But if it's the wheel coming apart and hitting the housing (from high turbine speed) . . then I can see that the shaft would break from that sudden decel. I think (If I learned anything in Design Machine Elements class this past semester anyway. . . ) that the accel/decel of the wheel could definately put stress on the shaft connecting the hot/cold side blades. (rotational acceleration=torque increase) But the accel probably wouldn't cause blade/fin failure itself? Can anybody check me on that one?



JR actually told me the HX40 would be ok if I kept the boost levels down. I was worried about not being able to keep them down with the bd6's. Because, I didn't think I could relieve the drive pressures enough with the wastegate, but he said he knows how to modify the turbo to get around that.



keep the info coming guys!!!!!!!!!!

 

[Hohn]

I've been told even a stock 40 will live at 38psi or less. I don't see how you could keep a 40 at 38psi or less at WOT with 200hp injectors! I can hit 32psi with just 75hp injectors.





I can't tell you what usually fails on a 40. All I've heard/read of usually end up with a broken shaft-- whether that shaft broke before or after the pinwheel hit the housing, who knows? You usually see a broken shaft and exploded pinwheel in both cases.



High drive pressure as EGT can cause the pinwheel's blades to weak at the attachment point (the root). This makes is likely to throw a blade and grenade the whole thing. Of course, a blade rubbing the housing would also cause failure.



I think that the shaft failures usually happen first due to acceleration/decelleration. But I'm no expert-- this is just my conjecture. I'd talk to JR more about this. I still think it's the weak shaft. Because of this, I'd think that a larger housing might be the ticket to help keep a 40 alive.



I'd run the 18 housing on the 40 and live with the lag if I had to have a 40.



A 40/18 from JR should live if taken care of, and the larger housing should give you a little more cushion in trying to keep down DP and boost with those showerheads.

 

[boydo]

I found the pdrhx40-16w to be a good turbo for my application I haven't been easy on it with all the toys on kill I see 43 psi @ manifold, normal driving with comp 3x5, lpg on, snow on I see about 38 psi @ manifold. It spools a little slower than the hx35, but wot makes up for it. If you got the hp bug consider a turbo that can be used in twins( pdrhx35, pdrhx40, b series, etc). I would recomemed one thing that you spent a little extra on a modified rather than a stock one.

 

[OPoole]

If you have the money go with a B1 turbo. .