[jat]

If you tried to let the turbo run high and control/bleed off pressure with the blow off valve, your turbo would have a very short life and likely end up in pieces, which could end up in your motor.. So the answer is no.

Bleeding of air should increase the load on turbine and therefore the turbine rpm should go down. Why should it overspeed?

Intercooler: The engines can be operated without intercooler. There are numerous engine without intercooler. The main function of intercooler is increase the charge density inside the combustion chamber so that more fuel can be burnt, that is, more power. Without intercooler means less initial cost and no loss of power due to fouling of intercooler later on.

[HPP]

Originally Posted by jat

Bleeding of air should increase the load on turbine and therefore the turbine rpm should go down. Why should it overspeed?

Intercooler: The engines can be operated without intercooler. There are numerous engine without intercooler. The main function of intercooler is increase the charge density inside the combustion chamber so that more fuel can be burnt, that is, more power. Without intercooler means less initial cost and no loss of power due to fouling of intercooler later on.

If you do not control the turbo with a wastegate, it will spin out of control. Bleeding off pressure on the compressor side(cool side) will have no effect(relatively) on the turbine side(hot side). You absolutely cannot do this, it will not work(it will be disastrous).

Engines can run without intercoolers, but it is not the optimal way. The main reason of an intercooler is to cool the intake air temps to fend off detonation. It is meant to save motors from dying, added power is a side effect. In the aftermarket world, intercoolers are used/needed when making more horsepower(you have to keep the intake air temps. as low as possible). And I have no idea what second part of your last sentence means, it makes no sense really.

[abhik]

"No. These are street cars driven on the street. The craze for horsepower here is insane. We have tuned cars to over 45psi in street trim.

A good friend of ours races his car at something like 65psi and about 1400hp."

ya! thats the reason i did'nt mention street cars as i know there are Jap tuners who tune and mod 350Zs, skyline GTRs, Lan-Evos to 1200-1400HPs so obviously they might be using turbos with a very very high boost range but i guess reliability would reduce and these cars cant be used for everyday driving right?

[HPP]

Originally Posted by abhik

"No. These are street cars driven on the street. The craze for horsepower here is insane. We have tuned cars to over 45psi in street trim.

A good friend of ours races his car at something like 65psi and about 1400hp."

ya! thats the reason i did'nt mention street cars as i know there are Jap tuners who tune and mod 350Zs, skyline GTRs, Lan-Evos to 1200-1400HPs so obviously they might be using turbos with a very very high boost range but i guess reliability would reduce and these cars cant be used for everyday driving right?

The life of the turbo and engine is definitely reduced when you are running over 45psi. But a lot of people do drive their cars up to about 40psi daily though. It will not last ten years and a 100,000 miles, but for most of us who make a lot of power, it lasts long enough to keep us satisfied. You have to expect certain things when playing this hard so, as long as things stay solid for multiple seasons, most are very happy with that. This year on my gsx the plan is to run 26-30 daily and over 30 on the weekends.

[dustDevil]

Originally Posted by HPP

If you do not control the turbo with a wastegate, it will spin out of control. Bleeding off pressure on the compressor side(cool side) will have no effect(relatively) on the turbine side(hot side). You absolutely cannot do this, it will not work(it will be disastrous).

So the best bet would be the combination of a waste-gate and a Blow-Off Valve!? Waste gate to control the spin-rate... and a BOV to ensure boost stays within limits under all conditions.

[doomsday]

Originally Posted by ananthkamath

Here's where I disagree. My source in Holset tells me that shaft sizing in diesel applications is much less critical (and hence smaller) because there is less chances of compressor surge than a throttled gasoline engine. Also, OEM turbochargers for gasoline engines usually have a turbine impeller and turbine housing material capable of withstanding much higher EGT.

Exactly. And thats the reason why turbocharged petrol engines do not generally use VGTs (apart from few exceptions like Pug 405, Porsche 996 tt) because the variable vanes on the turbine side are not upto the task of withstanding high EGT when compared to lower EGT of a diesel motor.

[HPP]

Originally Posted by dustDevil

So the best bet would be the combination of a waste-gate and a Blow-Off Valve!? Waste gate to control the spin-rate... and a BOV to ensure boost stays within limits under all conditions.

Yes and no. The Wastegate does all the boost regulation. The blow off valves purpose is to "blow off" or bleed off the pressure that is built when you get off the gas and the throttle body closes. When the throttle body closes you have a build up of pressure as well as a rebound of air bouncing back toward the turbo(in a sense). You do not want this kind of pressure coming back at the turbo, so the BOV is what bleeds off that pressure before it gets back to the turbo and damages it. So yes you'll always have a wastegate, and it's also best to always have a BOV. A lot of diesels(from the factory) however do not have BOV's so I will have to look into the theory there to figure out why they do not use them.

Originally Posted by doomsday

Exactly. And thats the reason why turbocharged petrol engines do not generally use VGTs (apart from few exceptions like Pug 405, Porsche 996 tt) because the variable vanes on the turbine side are not upto the task of withstanding high EGT when compared to lower EGT of a diesel motor.

That may be a reason, but not "The" reason. As is the case with ALL turbos, the technology since the early '90's has finally made them reliable. Before that turbos were very high maintenance and failed to often. They have finally made them where the general public is trusting them again. This is the case with the VGT's, it is early in the R&D for the VGT for general consumption. And in the relative future, we will see more and more in "petrol" cars driven by the general public. VGT technology is not new, but technology is finally at a point where making these to last is becoming a possibility.

The other reason why they are not widely used is cost, they are still extremely expensive compared to conventional turbos, thus most manufacturers can't justify putting them on most production cars.

[dustDevil]

Originally Posted by HPP

A lot of diesels(from the factory) however do not have BOV's so I will have to look into the theory there to figure out why they do not use them.

Well, that's probably be because Diesels do not have a throttle valve.

[overdose14]

Originally Posted by dustDevil

Well, that's probably be because Diesels do not have a throttle valve.

this is found when i was came to knew that in diesel cars acc cable is connected to pump.

[HPP]

Originally Posted by dustDevil

Well, that's probably be because Diesels do not have a throttle valve.

Probably correct. I do know however that there is a company in the states which has created a BOV that works on diesels.

[vibhu_f430]

I don't want to hijack this thread , But is there any Direct injection diesel from any manufacturer , where a turbo charger is not used ??

Ive never heard of a normally aspirated CRDI engine !!
Is it not mechanically possible ?

[HPP]

Originally Posted by dustDevil

Well, that's probably be because Diesels do not have a throttle valve.

Originally Posted by vibhu_f430

I don't want to hijack this thread , But is there any Direct injection diesel from any manufacturer , where a turbo charger is not used ??

Ive never heard of a normally aspirated CRDI engine !!
Is it not mechanically possible ?

Yes it is possible, and is done. I would have to do a little research to give you examples in cars, but I saw some direct injection diesels last week when I was touring the Lincoln Electric factory in Cleveland.(Lincoln Electric is a welding machine manufacturer.. I was taking a Tig welding class out there). They were part of the machines they make which have diesel engine generators which power their industrial welding machines.

[ananthkamath]

Originally Posted by HPP

Probably correct. I do know however that there is a company in the states which has created a BOV that works on diesels.

Are you talking about forge?

[HPP]

Originally Posted by ananthkamath

Are you talking about forge?

No, I'm talking about BD Diesel's Turbo Guard.

https://www.shopatron.com/index/532.0.19175.20188.0.0.0

STILLEN : BD Diesel TurboGuard (Diesel Blow Off Valve)

[Team_Godspeed]

Originally Posted by HPP

No, I'm talking about BD Diesel's Turbo Guard.

https://www.shopatron.com/index/532.0.19175.20188.0.0.0

STILLEN : BD Diesel TurboGuard (Diesel Blow Off Valve)

the turboGuard is for diesel trucks only ?

huh? You cant use a blow off valve in a turbo charger diesel car ? (SWIFT Vdi) Please explain why? the back pressure created when throttle is cutt has to be released through some where rite! Then what is the problem for the BOV used in petrol engine to be used in a diesel engine.