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

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

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.

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

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.

Possibly a good place to fit an EGT sensor could be the EGR fitting.....

Cheers Andrew

i wouldn't be too concerned with your boost pressure take a look at this site
http://www.berrimadiesel.com.au/turbocharging.html

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

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

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