Rb25 Not Making Very Much Power

[95_240]

Here are some combined posts from another forum that are describing my problems.

From other similar setups it seems that 400 whp should be acheivable.

So my car is at a tuner and from what I can remember he said my car is only making 246 whp at 12 psi and when he bumps it up to 19 psi it is only making 275 whp. He said at 246 at 6000 rpms the curve goes flat and at 275 at 6000 rpms the hp falls off. He also said the torque is very low. He also said that he is removing more fuel than he should have to because the car is running rich at higher boost and rpms. He believes there may be a restriction in the intercooler or exhaust. This is what is done to my car:

HX35 turbo
I believe the intercooler is a 3" but he said it might be 2.5"
Stock throttlebody
3" exhaust with a Y that goes to a qtp cutout and the other side to the stock muffler
Freddy intake manifold
750cc injectors
Aeromotive Stealth fuel pump
NGK heat range 7 plugs that are new
Adaptonic E420D
No boost leaks
Stock internals

New oem coilpacks, rebuilt turbo, and compression is 170 on all cylinders. I thought I might have some blowby but the tuner said it shouldn't have power that low with some blowby.

Today we bypassed the intercooler using straight pipe and that made no difference. Removed the exhaust and got up to 290 whp. Have a q45 throttle body laying around that we are going to try. I saw the dyno graph and it's at 5000 rpms that the power stops increasing and stays at 290 until 7000 rpms but the graph isn't a straight horizontal line during this period. The graph spikes up and down a little bit. The timing is correct and it sounds really good. I don't think the throttle body will make much of a difference but I don't have any other ideas. I never had the car dynoed when it had the stock turbo on it but I always felt like it didn't have much power at higher rpms kind of like what it is doing now.

Kind of a lame video. I didn't tell the tuner I was recording so I wasn't going to take a video of him without his permission. I think everything sounds good unless someone has another opinion. Don't hear any misses or anything like that.

Couple of quick questions.

Does 290 whp seem in the ballpark for 5000 rpms with this setup?

Also is it a possibility that the vct is bad and not deactivating? I guess when I check timing during a dyno pull that would eliminate a bad cas and vct. I'll do that tomorrow and report back.

I also have a weird problem when the car is first started it has to be revved up to 2000 rpms a few times before the alternator starts charging. It is a quest alternator that I had rebuilt. Not sure if this is related at all just disclosing.

Thanks for any help.

[KiwiRS4T]

Don't know what it should make. Don't bother changing throttle body.

Do a run with VCT on and another with it off - that will tell you if it is working and also help to set the change-over point.

[95_240]

From some of the dyno sheets I've seen with similar setups people are averaging around 420 whp with the same mount of boost I'm running. They we're around 300 at 5000 rpms so it seems like my car is making power fine until then and then it just stays at 290.

[scotty nm35]

So he thought it might be the exhaust, but you couldn't drop two bolts on the dyno to make sure?

I vote a collapsed cat or some serious restriction in the exhaust.

[Plattsy]

So he thought it might be the exhaust, but you couldn't drop two bolts on the dyno to make sure?

I vote a collapsed cat or some serious restriction in the exhaust.

this.

[95_240]

I don't have a cat and I did remove the exhaust. That got it up to 290 whp.

[DoseVader]

Does any one have any info on this HX35 turbo as I have never heard of it and it could be your problem?

Edited March 16, 2015 by DoseVader

[95_240]

Supposed to be similar to a gt35 I think. Plenty of people in the states get over 400 whp with this turbo.

[AngryRB]

Just couple of suggestions

Air is leaking out eg. an ill fitting intake manifold so 19psi become 12psi and need fuel taken out?

Alternator should be replaced with a stock unit?

[zebra]

Supposed to be similar to a gt35 I think. Plenty of people in the states get over 400 whp with this turbo.

There are about 3 million different variants of the HX35.

Only about 2 of them are any good in a performance application.

[95_240]

Air leaking between the intake manifold and the head could be a possibility but a boost leak test showed no leaks. The quest alternator is a common upgrade in the states because of the higher amp output. I had it rebuilt and they probably only replaced the brushes so I guess the voltage regulator could be on the way out.

Ok so there are only two variants of the hx35 that are popular that came on the dodge diesel truck and those are what everyone uses. 7 blade or 8 blade. I'm using the 7 blade which will allow more power but both versions will get me where I expect to be.

[Dobz]

Just at a quick search it looks as though the hx35 is designed for 5-6.5 diesels with many design and specification differences. I can't find wheel sizes on Holset's site but from what some diesel forums say they use a 60mm ex. with an in. wheel varying from 54mm up to 78mm.

[95_240]

Here is more about the holset turbos. http://www.sau.com.au/forums/topic/247809-holset-turbos/

I'm running a divided manifold. The turbo is not the limiting factor in my setup.

HX35:

The 8blade hx35 has a 56mm compressor inducer. This is found on 1995-1998 cummins manual pickups. The compressor flows 52 lb/min according to the compressor map. The bolton BEP housing (0.55 a/r) is enough to push the limit of the compressor. There's several 500whp 8blade hx35 cars out there with the bolt on housing. It reaches 20+psi by 3500rpms in 3rd with 272 cams. Smaller cams would equal a faster spool speed in most cases.

The 7blade hx35 has a 56mm compressor inducer. This is found on the 1999-2002 cummins manual pickups. The compressor flows 60lb/min according to the compressor map and logged results from a member here. The bolton BEP housing with the hx35 turbine wheel do not SEAM to have enough flow to really reach the potential of 60lb/min. But many have logged over 50lb/min so far and seen 500whp. The stock hx35 12cm^2 twinscroll turbine housing is a t3 flange housing. This mated to a NON-divided runner manifold has produced a 132mph trap speed with a full weight 1g AWD. This is about 600whp. So the flow is there with the stock housing if you use a non-divided manifold. The spool speed of the 7blade hx35 is similar to the 8blade hx35 with 20+ psi by 3500rpms in the bolton housing and by 4000rpms with the stock housing with a non-divided manifold.

[Guilt-Toy]

sounds retarded.....

[XRATED]

...

I have to say it... Nitrous Fixes Everything!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[jay-rod]

Sounds like the Turbo is running out of puff.

[95_240]

Here is the latest dyno 336 whp 295 ft-lb torque. This is on a mustang dyno.

This is the ve map which seems too flat.

Here is the ignition map.

I told him that the vct should be deactivated below 5000 rpms but I did a log and it is activated until 8000 rpms so this is probably where I'm losing some power now but I'm not sure how much that will add. I'm having some problems with my charging system but once that is fixed I'll take it back to get the higher cells retuned with the vct off and hopefully that will solve some of the problems.

I have a log on adaptronics forum if anyone cares to look.

Thanks.

[Dose Pipe Sutututu]

I just did

Your VCT is enabled all the way to redline, perhaps try only setting at 100% between 1500rpm & 5000rpm (as a test). Of course doing 2x runs and finding the intersection point is more ideal - but I'll leave that up your tuner to decide on.

[KiwiRS4T]

I would have thought doing 2 runs was the quickest (cheapest) way to find the changeover points.

[95_240]

I've read that two runs is the best way to find the changeover point and I was positive 5000 rpms was the max you would want to change it over on stock cams that's why I threw that number out there. The base map actually had it deactivated at 5000 rpms but that is when it was making less power. I don't know if that was related or if something else was going on because somehow it gained power with it activated to red line. When we talked about the vct on the base map I misunderstood him and thought he said it was activated at 5000 rpms and he deactivated it but it was the opposite.

It sucks that the tuner is an hour and a half away otherwise I could have been there and discussed all the settings the first time instead of having to take my car back.