Hi there,

I just wondered if anyone knew what maximum boost pressure is safe to run on a 1721cc Turbo engine ('95 460 Turbo) until the fuel supply is in danger of running low. I have just purchased a Manual Boost Controller, and it works a treat, but I don't want the engine to run lean, as obviously that's gonna hurt it somewhat!!

At the moment, I have it set so that the needle on the original boost guage sits at a fraction below the red region at full throttle.

Many thanks,

Kindest regards,

Crispin Hall

 

I think 15psi is the max.If I remember correctly.I have heard people running 15psi on stock engines.

 

Sir, that's a great help. Thanks very much. I think mine's running at about 0.7-0.75 bar, (around 10.5 psi) so it should be safe then!![sm=smiley1.gif]!!
However, if it is safe to run the stock setup at 15psi, which is just over 1 bar, then how come the power to the injectors is cut at 0.9 bar, which is several psi lower. And the red region on the original boost guage starts (so I've been told) at 0.75 bar (10.9psi) so is it therefore safe to run the boost slightly into the red without my engine running lean? I don't want to melt my pistons you see!! That would be bad!

Is is just a precaution to scare people into not overboosting, or would running the boost at just below 0.9 bar (13psi) be bad for the car?

Once again, many thanks for your time,

Regards,

Crispin

 

I have a buddy that was running between 12 and 15 psi with nitrous.And no problems at all.

 

Sorry to bother you again, just one more question!! I've disconnected the black and red hoses, (both connected to the solenois valve) and have effectively replaced the solenoid valve with the MBC. I've just read on another forum that you get better results leaving the solenoid connected, inline with the MBC, and placing the MBC along the red hose (in between the solenoid valve and the wastegate actuator). Out of interest, why would this be?

I thought at first it may be so that the ECU is not left 'out of the equation' potentially allowing the risk that if it did overboost, the ECU would not know to cut the power to the injectors. But I thought there was a separate boost sensor connected to the ECU?! I can't see why leaving the old electric solenoid valve in series with the MBC (fitted between it and the wastegate) would give any benefit.

Would be glad to know!!

Many thanks for your other quick replies, hope to hear from you.

Regards,

Crispin

 

I believe it would be so the computer can adjust the fuel so that in boost it won't run lean.Any sensors that are there the computer uses the signals for something.

There might be an easier way to explain it but im not sure.I normally don't mess with boost controllers.My knowledge is pretty short of them.

 

OK, thanks very much for your prompt reply!! I will probably try and try and connect it back up tomorrow then in that case.

Thanks ever so much for your time - will try not to bother you again!!

Kind regards,

Crispin

 

Let me know how you make out.Try driving it both ways and see what the diffrence is.

 

It would appear that it's slightly better, but then that could just be psychological, as I suppose I don't want to think I wasted all of 44p on some hose!! But I've actually turned down the boost, as it seems to run just as well (if not better) and seems to be just as quick as it was at higher boost without the solenoid in line with the MBC.

It is possible that it does make a difference, but it could also be the fact that the hose I used to connect the MBC to the wastegate this time round is shorter than the original hose, so it may just be responding better.

I would go with this way being the better way though, but like I said, it could jsut be psychological!? All I know, is that I need to make a cold air feed to my new filter, as when sat in traffic, it doesn't seem to like it so much!!

Regards

 

Yes they run funny off of warm air.They love nice cold air.

 

Hi there,

Just to say, I've sorted out the hoses, so they all nice and neat now, and are all straight - no stupid bends or kinks like I had before, and I've actually lowered the boost slightly so that it sits about 2mm below the red - probably somewhere around 9psi, and it's running absolutely superbly. Really really responsive, the boost doesn't jump around so much now, it's far more stable. It seems to be quicker than it was before, and sounds far far sweeter - a lot more grunt. I think that it may have been a little too much boost before, and the ECU was retarding the ignition (I've heard it can do this). So I don't know whether it's because I've lowered the boost, or because I've shortened the hoses, or because I've repositioned the MBC in between the wastegate and the old solenoid valve, but it's running really well. A great surprise. Mind you, it's a pretty cold night, so may be it's the cold air that's making all the difference?!?!!? Who knows!!

 

Im glad you got it running really good.Enjoy it.

 

Now that everything's running well, I'm now worried about the air filter, and the fact that it's a stainless steel mesh, which will not provide as much filtration as a stock air filter. I just wondered how important this is. Obviously you don't want foreign particles in the engine at all, but nothing bigger than a dust particle could really get in, but then stock air filters are designed to keep even those out!! Is running a racing filter on my engine, with perhaps slightly lower quality filtration going to cause damage to it, or make it wear much faster? Obviously I will be changing the oil every 4-5000 miles or so, but will tiny particles just be burnt up, or will they wreck my engine?

Regards,

Crispin

 

What kind of filter are you running?

 

It's a stainless steel cone filter from www.turbobits.co.uk/acatalog/air_filters.html
I think it is made by "MAX Racing."

 

I have never heard of any problems from running that kind of filter.Some say it allows more dirt in but I don't believe it.