Excessive boost on 1HZ after 3" exhaust???

Submitted: Wednesday, Jan 25, 2006 at 23:44
ThreadID: 30120 Views:12601 Replies:9 FollowUps:4
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Hi all, I have put a 3" exhaust system on my after market turbo-ed 1HZ. Prior to this (std exhaust) I was cranking out 10.5lbs boost (11.5 with heavy trailer up steep hill in 3rd with foot flat). Now I am getting 13.5lbs very easily and last week noticed just short of 15lbs with trailer. I reckon this is way way to much and will adjust the waste gate to get it back to 10.5lbs.

Is this normal to get such a large increase in boost after fitting a larger free flow exhaust (Note that I'm not talking about spin-up time, just max boost)?? Could it be that the waste gate wasn't opening before exhaust upgrade, that the old exhaust was so restrictive that the turbo just couldn't blow that hard or is there something else I should be looking at? I didn't adjust the pump for the new exhaust - only when the turbo went on some 150 thousand k's ago.
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Reply By: Member - Donald_L - Thursday, Jan 26, 2006 at 00:39

Thursday, Jan 26, 2006 at 00:39
With less back pressure the exhaust gasses will expand with ease in the exhaust turbine giving a higher kenetic energy transfer & subsequent power to the air compressor,
This gives the ability to raise the discharge pressure. There will be a need to watch the boost does not become too excessive as combined with the increase flow through the exhaust turbine ther will be localised elevated temperatures in all of the turbo charger. Hence cooling & lubrication can become critical. There may also be need to introduce a turbo timer if not fitted. Sounds like you are on the right track to set up the waste gate, but for my money I would get it on a dyno & monitor all changes in temperature.
The last thing you want is a fire or a lube failure, Especially climbing a hill in the bush.
Good Luck
AnswerID: 150973

Reply By: Member - Ian H (NSW) - Thursday, Jan 26, 2006 at 07:31

Thursday, Jan 26, 2006 at 07:31
When I fitted my turbo to a 1HZ I was advised to leave the standard exhaust system to avoid the very same problems that you are experiencing and so far it has been the case. I get 136KW and about 390NM with no change in the fuel economy.
AnswerID: 150993

Reply By: Big Woody - Thursday, Jan 26, 2006 at 07:44

Thursday, Jan 26, 2006 at 07:44
Hi Tony,

Wow am I glad you posted this question.

I have a 1991 80 series with 1HZ and aftermarket mike Vine turbo fitted since new (285000 k's) and it goes great.
It has a standard exhasut system and goes quite well but I have just been looking into having a 3" mandrel bent exhaust fitted in the next few weeks. I thought with less restriction I would have gained a bit more power but I hadn't thought of the higher boost levels and exhaust temperatures which from my research have seen the death of a few 1HZ's with turbo's fitted.

Maybe the motor will last longer using the exhaust as a limiter to prevent things from getting too high.

I will watch this thread with interest.

Brett
AnswerID: 150995

Reply By: 120scruiser - Thursday, Jan 26, 2006 at 12:34

Thursday, Jan 26, 2006 at 12:34
If you are running that much boost on a 1HZ you are asking for trouble.
I would be dropping your boost down to around 7-8lb and for godsake fit an egt guage.
Have a good read of this site as it is in plain engish
www.bankspower.com
Special thanks to Kesh for that site.

AnswerID: 151064

Follow Up By: Member - Donald_L - Thursday, Jan 26, 2006 at 14:34

Thursday, Jan 26, 2006 at 14:34
Howdy,

For me & I'm sure for others to install a stand-alone tapping point for a pyrometer upstream of the t/charger in the exh manifold for an egt is a pain in the butt if a stripdown is required. I have a question you may be able to answer.
Do you know of any kits or methods that may be used to Tap into the OEM,s control system to pick up their sensors of exhaust temp & repeat it on a gauge.digital display ?? Wish I could get a schematic control drawing of my GU 3.0TD

another good site similar to bankspower is www.thermogaurd.com.au

regards Donald
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FollowupID: 404660

Follow Up By: 120scruiser - Saturday, Jan 28, 2006 at 13:40

Saturday, Jan 28, 2006 at 13:40
Both Gregorys and Haynes manuals have full electrical schematics in them.
No fault codes though.
Ian from thermoguards site is good and a great product. I fitted one to my 1hz 80 series when I had it. The only drama was when I sold it the new owner new it was there, he was a friend, and wouldn't let me take it out.
I recommend them to all my customers when I fit turbos.
As for your question of tapping into the electrics. Dunno.
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FollowupID: 405090

Follow Up By: Ian from Thermoguard Instruments - Monday, Jan 30, 2006 at 10:57

Monday, Jan 30, 2006 at 10:57
Hi Donald L,

Tapping into the vehicle's original EGT sensor would be a great idea -except that it doesn't have one... At least, the GU Nissan ZD30 engine doesn't, from the information I have on it's ECCS-D Engine Control Module. Nor am I aware of any common passenger vehicle turbo-diesel engine which does. Only heavy trucks and earth moving/agricultural equipment seem to have them as standard. If anyone knows of a light vehicle with a standard EGT sensor, please let me know.

120scruiser, thanks for the kind words.

Ian
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FollowupID: 405339

Reply By: bombsquad - Thursday, Jan 26, 2006 at 16:29

Thursday, Jan 26, 2006 at 16:29
Possibly a good place to fit an EGT sensor could be the EGR fitting.....

Cheers Andrew
AnswerID: 151101

Reply By: luch - Thursday, Jan 26, 2006 at 18:15

Thursday, Jan 26, 2006 at 18:15
i wouldn't be too concerned with your boost pressure take a look at this site
http://www.berrimadiesel.com.au/turbocharging.html
AnswerID: 151123

Reply By: Ian from Thermoguard Instruments - Monday, Jan 30, 2006 at 11:38

Monday, Jan 30, 2006 at 11:38
Hi all,

I do think the boost pressure control needs looking at. Regardless of the boost setting chosen for a particular engine, it should be regulated to that maximum setting by the wastegate mechanism. If the maximum boost pressure is wandering around all over the place, I'd get the wastegate looked at.

Perhaps what might have happened is something like this: with the old exhaust restriction, the wastegate may have never needed to open fully and it might be a bit carboned-up at near the fully open position. Now, with the low restriction exhaust, it needs to open up further to regulate the boost pressure, but it can't.

All that said, the higher boost pressure shouldn't do any harm, as long as the fuelling isn't increased along with it (I'm assuming you still have the original non-compensated injection pump). More air, with the same maximum fuel delivery, will actually lower the peak EGT levels, as is implied on the Berrima page referred to above. A greater concern would be that, if the wastegate is faulty, it might stick open and not allow the normal boost pressure to be developed. In this case, at full load, the maximum fuel quantity will be delivered into a less than full mass of air, leading to excessive EGT and potential damage.
Ian
AnswerID: 151743

Reply By: Ian from Thermoguard Instruments - Monday, Jan 30, 2006 at 11:47

Monday, Jan 30, 2006 at 11:47
Hi all,

I do think the boost pressure control needs looking at. Regardless of the boost setting chosen for a particular engine, it should be regulated to that maximum setting by the wastegate mechanism. If the maximum boost pressure is wandering around all over the place, I'd get the wastegate looked at.

Perhaps what might have happened is something like this: with the old exhaust restriction, the wastegate may have never needed to open fully and it might be a bit carboned-up at near the fully open position. Now, with the low restriction exhaust, it needs to open up further to regulate the boost pressure, but it can't.

All that said, slightly higher boost pressure shouldn't be a problem, as long as the fuelling doesn't increase along with it (I'm assuming you still have the original non-compensated injection pump). Running the normal maximum fuel delivery with slightly more air will actually lower peak EGT. A greater concern would be if a faulty wastegate sticks fully open and normal boost pressure cannot be achieved. Then, at full load, the maximum fuel charge will be combusted in less than the appropriate mass of air, leading to excessive EGT and potential damage.

Ian
AnswerID: 151746

Reply By: Ian from Thermoguard Instruments - Monday, Jan 30, 2006 at 11:48

Monday, Jan 30, 2006 at 11:48
Hi all,

I do think the boost pressure control needs looking at. Regardless of the boost setting chosen for a particular engine, it should be regulated to that maximum setting by the wastegate mechanism. If the maximum boost pressure is wandering around all over the place, I'd get the wastegate looked at.

Perhaps what might have happened is something like this: with the old exhaust restriction, the wastegate may have never needed to open fully and it might be a bit carboned-up at near the fully open position. Now, with the low restriction exhaust, it needs to open up further to regulate the boost pressure, but it can't.

All that said, slightly higher boost pressure shouldn't be a problem, as long as the fuelling doesn't increase along with it (I'm assuming you still have the original non-compensated injection pump). Running the normal maximum fuel delivery with slightly more air will actually lower peak EGT. A greater concern would be if a faulty wastegate sticks fully open and normal boost pressure cannot be achieved. Then, at full load, the maximum fuel charge will be combusted in less than the appropriate mass of air, leading to excessive EGT and potential damage.

Ian
AnswerID: 151747

Follow Up By: Ian from Thermoguard Instruments - Monday, Jan 30, 2006 at 11:51

Monday, Jan 30, 2006 at 11:51
Sorry about the double reply, peoples. My browser came back with an error message the first time and I thought I'd lost the original reply.
Ian
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FollowupID: 405349

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