Where's my boost?

Submitted: Friday, May 30, 2008 at 20:28
ThreadID: 58191 Views:3749 Replies:4 FollowUps:8
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Hi all,
My turbo is rather sick. It's an aftermarket Denco on a 1HZ 105 series 'cruiser. I think I've had the problem for a while as my boost has always been low at around 5 psi. Anyway, I recently fitted a Denco water to air intercooler, which came complete with a replacement high boost wastegate actuator. Flat out, can't get more than 4.5 psi boost, even with the actuator pipe disconnected.

Had the injectors done and pump checked out this week. A run on the dyno confirms my problem. Tomorrow, I will remove the turbo assembly and check it out physically to look for possible causes.

In the meantime, I wonder if anyone else here has experienced a similar issue, particularly if you have the same brand hairdryer? If so, what did you find? I have a few theories, but perhaps someone else has been there before me.

Any helpful suggestions or ideas will be gratefully accepted.

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Reply By: Member - Barnray (NSW) - Friday, May 30, 2008 at 21:07

Friday, May 30, 2008 at 21:07
If you can open your exhaust in front of the mufflers and test drive.Barnray
AnswerID: 306829

Follow Up By: GerryP - Friday, May 30, 2008 at 21:18

Friday, May 30, 2008 at 21:18
Good suggestion Barnray, but took the muffler off a couple of weeks ago. Can see straight through, so no problem there. You've got me wondering though, had a snorkel fitted by others a while back. Is there anything under the gaurd area that could restrict airflow if not fitted properly? It's a Safari jobby.
FollowupID: 572719

Reply By: Member - Barnray (NSW) - Friday, May 30, 2008 at 22:05

Friday, May 30, 2008 at 22:05
Is your exhaust standard or has it been opened up and has pump been adjusted to suit turbo, is the turbo the correct one.I have fitted 2 turbo's from ground up, even made up a ex manifold for one and run about 10psi boost on a 2.4 Toyota. Air plus fuel =heat needs more room to flow in and out. B
AnswerID: 306850

Follow Up By: Member - Barnray (NSW) - Friday, May 30, 2008 at 22:07

Friday, May 30, 2008 at 22:07
Check cat converter. B
FollowupID: 572729

Follow Up By: GerryP - Friday, May 30, 2008 at 22:18

Friday, May 30, 2008 at 22:18
Exhaust is 2.5 inch straight through. No cat converter.

Turbo was on the car when I bought it, but is proper kit for the 1Hz. Fuel is actually a tad on the rich side as EGT runs high under load. However, this should come down once I get some boost and hence more airflow. Dyno figures show air/fuel ratio to be OK.

I'm actually hoping it is something simple like a crack in the wastegate, but could be stuffed vanes or even stuffed bearings not letting it wind up. Guys at the dyno (Hi-Tech Diesel) suspect actual turbo but can't tell without taking it off the car and inspecting it.

I'm OK mechanically so will whip it off tomorrow for a look see.

Just thought that perhaps there may have been someone else out there that had experienced something similar.

Thanks for your suggestions though Barnray - always helpful
FollowupID: 572737

Reply By: awill4x4 - Friday, May 30, 2008 at 22:46

Friday, May 30, 2008 at 22:46
Gerry, if you still have the original crossover piping remove your Denco intercooler and fit it back on to check to see what your boost pressure now runs at.
If your I/cooler is the 4" one I think that could be the cause of your restriction as the number of tubes that the air flows through isn't many at all. I would love someone to measure the boost pressure both before and after the I/cooler on those 4" ones, I suspect a high boost loss running those.
If you're measuring your boost pressure at the inlet manifold and you turbo has a fitting in the compressor outlet then measure your boost there. If it has significantly higher boost out of the turbo compared to the inlet manifold then it's a restriction in the intake side therefore it's definitely the I/cooler causing the restriction.
It makes you wonder why Denco supply a "replacement high boost actuator" in the 1st place. Perhaps they already know the I/cooler is poorly matched to the engine displacement.
Regards Andrew.
AnswerID: 306857

Follow Up By: GerryP - Friday, May 30, 2008 at 22:53

Friday, May 30, 2008 at 22:53
Yes, I suspect the intercooler does has a fairly high pressure drop and it is something I have wondered about myself. However, Denco do seem to have a reasonably good name so I have assumed that since the i/cooler and turbo are supossedly matched to the car, that the turbo should be able to cope - but, perhaps not? I do have the old bits, so that is something I could try.
FollowupID: 572739

Follow Up By: awill4x4 - Saturday, May 31, 2008 at 00:04

Saturday, May 31, 2008 at 00:04
Gerry, before you start pulling turbo's etc off try to measure your boost pressure before the intercooler it really wouldn't surprise me one bit if the I/cooler is the problem and if that's the case I would be asking for my money back.
When you look at the number of tubes even in a factory I/cooler and compare them to the 4" diameter one it's very apparent which one will flow boosted air better.
Regards Andrew.
FollowupID: 572749

Reply By: Thermoguard Instruments - Sunday, Jun 01, 2008 at 11:28

Sunday, Jun 01, 2008 at 11:28
Hi Gerry,

I'd suggest starting with the basics.

First, is your boost pressure really 4.5 to 5 psi? Is you gauge accurate? Can you borrow another gauge from someone and substitute?. Or put yours on another vehicle temporarily to check it?

If the gauge is reading correctly, is the connection to the sensing point clear and free of leaks?

Once satisfied that the gauge is telling the truth and you really do have low boost, the next thing to check for would be inlet restrictions.

Visually check that all is completely clear from the snorkel inlet to the turbo compressor inlet. If you can't physically see through any section, stick a stiff wire down it to make sure nothings stuck inside. Is the air filter element OK? Are any flexible hose sections gone soft and sucking in under load?

Also, hoses and rubber elbows etc. can and do delaminate and can partially or completely block the duct while looking perfectly OK from the outside. (it's happened to me and had both me and the RACQ mechanic stumped for the best part of an hour before we found it!)

Does the turbo compressor wheel turn quite easily rotating it with your finders? It should have very little noticeable radial movement but a bit a axial 'play' is normal.

If the boost sensing point is downstream of the turbo, I'd suggest relocating it to the turbo air outlet (generally they are tee-ed off the wastegate actuator hose) and see if you get a higher reading. If so, there is a severe restriction between the turbo and the inlet manifold. Again, flexible hose sections would be prime suspects.

If your boost sensing point is at the turbo air outlet AND boost is still low AND you’re sure the exhaust system is completely clear AND all the above is OK I suspect the wastegate is faulty - probably the flap or seat or both badly burned and eroded.

Please let us know what you find.

AnswerID: 307081

Follow Up By: GerryP - Sunday, Jun 01, 2008 at 19:31

Sunday, Jun 01, 2008 at 19:31
Thanks for your reply and input. It still has me baffled I'm afraid.

The pressure for my gauge is taken after the water-to-air intercooler, just as it enter the inlet manifold so it is measuring pressure at the engine and at that spot is definitely 4.5 psi. The diesel place also confirmed this. Thinking the intercooler may be the cause, I measured the pressure just after the turbo and before the intercooler and made barely 1 psi difference - so that eliminates the intercooler.

To eliminate snorkel intake problems, I ran (not very long!) with the air cleaner box open and no filter - no difference.

I had already removed and checked the muffler a few weeks back, so that is OK. It's a 2.5" aftermarket pipe with nothing else in it.

All hoses are really short as the intercooler sits where the cross-over pipe normally goes, but all check out OK.

Yesterday, I removed the turbo assembly for a visual inspection. The wastegate mechanism looked OK, but I lapped it in a bit anyway, just to be sure. No excessive play in the bearings.

I removed the housing and found no signs of binding or rubbing although the clearance between the wheel and housing was a tad more than I expected, but that's probably just me.

The only thing I'm not sure about is what the bearings should feel like as they are oil type fed from the engine oil pump. While the wheels spin freely and smooth, they don't seem to run on for long. Could it be that the bearings are binding somehow and not allowing it to spin up to full speed?

Anyway, put it all back and physically "wired" the waste gate shut so it can't move, just in case the actuator is faulty and took it for a run. Bugga - still the same!

When driving, the boost starts to come up when expected, but gets to 4.5 and just stops there.

Might go back to the diesel people and see whether it's worth me taking it out again and having them take a look?

Anyway, thanks again for your interest.


P.S. The EGT gauge is working great! (free plug :)
FollowupID: 573044

Follow Up By: Thermoguard Instruments - Monday, Jun 02, 2008 at 06:18

Monday, Jun 02, 2008 at 06:18
Hi Gerry,

Strange one indeed. Yor initial post says "I think I've had the problem for a while as my boost has always been low at around 5 psi." Have you spoken to Denco about this previously? It's a long shot I know, but perhaps you've had a faulty turbo from day one?

I know it's not likely but maybe it was assembled incorrectly from the factory (with wrong size exhasut turbine for that size housing, for example)? Other than this, I'm out of ideas.

Please keep us informed.
FollowupID: 573151

Follow Up By: GerryP - Monday, Jun 02, 2008 at 23:45

Monday, Jun 02, 2008 at 23:45
Hi again (Ian from memory?)
You know, it's interesting, as that is precisely what I did today. Spoke to a guy at Denco who was really helpful. I need to get back to him with some casting numbers, but we may be a bit closer.

Apparently, there is an older model turbo for the 1HZ which was made before the company supplied the barrel type intercoolers. This turbo's maximum boost was only around 8 psi with the actuator set to 7.5psi. Therefore, if I happen to have one of these, and now with the intercooler fitted, I'm behind the eight ball, especially if mine's not that efficient any more. Since my car is a '99 and the kit was already on it when I bought it, this may well be the case.

However, all is not lost, as they subsequently made changes to the turbine housing (I think the wheel is still the same), which improved its performance by several psi. This overcame the drop across the intercooler and gave a couple of psi in reserve. I can apparently upgrade mine quite easily. (Don't know $$'s though!)

All I want is 7 - 8 psi... we live in hope!

Going away this weekend so I probably won't know anything until some time next week, but I've got all fingers crossed.


FollowupID: 573273

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