forward facing turbo question? Why no buicks?

[driven87]

I was wondering on another race site and there was a post with pics from a track event and there was alot of turbo cars. I noticed just about all the turbo cars has the turbo facing the front of the car and had a hole in the bumper with a large pipe feeding the turbo. Now i have read in the archives on here that cold air intakes are not even needed on these cars and putting the filter in the engine bay is fine. Why do these guys have this kind of setup and can a slower car benifit from maybe having a hugh 5" pipe routed right to the turbo inlet? I'm talking just track here i know it would be bad for street driving. Curious as to why i dont see any buicks with straight pipes going to the inlet? Thanks for letting me think out loud.

 

[Just a Six??]

My friend that is on here & well known did ONE pass with filter & pipe off & it cost him a Turbo! Not worth the risk or cool factor IMO.
Now, IF your John Force Racing then you have 50 turbo's & who cares??

 

[GW2]

I think its because the engine bays are smaller in those cars so they benefit more form the cold air intake. and they usually still have a filter.

 

[CamoDeafie]

think of it this way; with a very good intercooler, what is the reason for sticking the air filter out to outside or to the bumper area? were it a hot air turbo, it wouldnt matter as well; because of the fact that you're compressing air, which heats up regardless...(in a non-intercooled situation)

also, these buicks, have very generous engine bays; and as such, packaging isnt as much as an issue as the other turbo cars.... now, if one were to make it look like the car doesnt have a turbo, what better than putting the turbocharger system right between the radiator and the bumper? (other than the clear fact it;ll be subject to abuse from speedbumps if one is not careful in packaging it..) and routing a stock looking air tube from the intercooler?

anyways; its not needed when you;ve a charge cooling system that helps alot; and its just plain stupid to expect it to help when you dont have a charge cooling system...

 

[Dusty Bradford]

To put a turbo in the grill like you see on a lot of race cars requires the radiator to be relocated.

There are 2 issues with this. Most of the Buick crowd are the "buy it and bolt it on" crowd as is 90% of car enthusiast. To put a turbo in the grill would require all custom built pieces.

The other issue. Race class rules. The most well known race classes in the Buick world specifically ask for the turbo to be in the stock location. Personally I hate that rule. I think it would be cool to allow the Buick crowd to spread out into other orgs without being penalized. That's the whole problem with the Buick class racing. If anything looks any different from another car and that car runs well, it's automatically assumed the turbo location or whatever is different is the reason the car is faster.

Here's what it would look like

 

[driven87]

I guess im asking since they are putting them up front im guessing there is SOME benefit to it. I even saw some that had huge piping going from the front bumper right into the turbo inlet for a straight shot of cold air. I understand the class racing etc etc im just wondering if the guys out there with no rules in other classes are doing it there has to be a reason somewhat. Maybe ill have to try a 6" pipe going from the bumper to the turbo and try it out since moving the turbo to the front is not an option anytime soon, lol.

 

[Bent6]

To put a turbo in the grill like you see on a lot of race cars requires the radiator to be relocated.

There are 2 issues with this. Most of the Buick crowd are the "buy it and bolt it on" crowd as is 90% of car enthusiast. To put a turbo in the grill would require all custom built pieces.

The other issue. Race class rules. The most well known race classes in the Buick world specifically ask for the turbo to be in the stock location. Personally I hate that rule. I think it would be cool to allow the Buick crowd to spread out into other orgs without being penalized. That's the whole problem with the Buick class racing. If anything looks any different from another car and that car runs well, it's automatically assumed the turbo location or whatever is different is the reason the car is faster.

Here's what it would look like

I agree 110% about the Buick class rules. We are contemplating building a 25.3 spec drag radial car so we can run some EZ street and other 10.5 classes and would like to be able to run in TSO but the rules are too restrictive for what I have in mind building. I seriously doubt a forward facing turbo offers much if any of a performance advantage.

 

[turboc87gn]

:biggrin:

 

[Dusty Bradford]

I agree 110% about the Buick class rules. We are contemplating building a 25.3 spec drag radial car so we can run some EZ street and other 10.5 classes and would like to be able to run in TSO but the rules are too restrictive for what I have in mind building. I seriously doubt a forward facing turbo offers much if any of a performance advantage.

It's been tested and found the forward facing turbo's do offer a little gain. Backpressure readings are lower at the same boost level from having to work the turbo less. Not a huge gain, but some.

If I were building a Stage 2 car it would have a forward facing 80mm on it with a liquid intercooler to run the 275 radial stuff. If it didn't fit TSO...so be it.

 

[turboc87gn]

think of it this way; with a very good intercooler, what is the reason for sticking the air filter out to outside or to the bumper area? were it a hot air turbo, it wouldnt matter as well; because of the fact that you're compressing air, which heats up regardless...(in a non-intercooled situation)

also, these buicks, have very generous engine bays; and as such, packaging isnt as much as an issue as the other turbo cars.... now, if one were to make it look like the car doesnt have a turbo, what better than putting the turbocharger system right between the radiator and the bumper? (other than the clear fact it;ll be subject to abuse from speedbumps if one is not careful in packaging it..) and routing a stock looking air tube from the intercooler?

anyways; its not needed when you;ve a charge cooling system that helps alot; and its just plain stupid to expect it to help when you dont have a charge cooling system...

You must not have owned many turbo cars...There is a difference in having your turbo inlet in cooler air vs hot engine bay air..You ever drive you car on a hot summer day and it feels normal but then when night comes and the air is cool and dense all of a sudden you car seems to have more seat of the pants kick than usual? You never heard the phrase "this is turbo weather"? your intercooler didnt all of a sudden become that much more efficient its the combination of cooler inlet air and cooler air passing thru the intercooler that causes this mysterious phonomenon

 

[Bent6]

If I were building a Stage 2 car it would have a forward facing 80mm on it with a liquid intercooler to run the 275 radial stuff. If it didn't fit TSO...so be it.

Yeah - I'm ready to do something different and want to stay with the Buick V6 just to be different. I really wish they would drop the stock inner frame rail rule and stock turbo orientation on the TSO rules. The tire size rule would take care of the inner frame rail issue and enable a guy to tuck the tires UNDER the car and the turbo orientation would open up some creativeness in the engine bay.

Most of the Buick race classes are too cookie cutter IMO and limit innovation. However, as you stated above, cookie cutter is OK with 90% of the population. A lot of sanctioning bodies are finally starting to give decent weight breaks for the V6 after all these years. It just doesn't make sense to build a car that is limited to only one class and/or sanctioning body.

 

[Dusty Bradford]

Yeah - I'm ready to do something different and want to stay with the Buick V6 just to be different. I really wish they would drop the stock inner frame rail rule and stock turbo orientation on the TSO rules. The tire size rule would take care of the inner frame rail issue and enable a guy to tuck the tires UNDER the car and the turbo orientation would open up some creativeness in the engine bay.

Most of the Buick race classes are too cookie cutter IMO and limit innovation. However, as you stated above, cookie cutter is OK with 90% of the population. A lot of sanctioning bodies are finally starting to give decent weight breaks for the V6 after all these years. It just doesn't make sense to build a car that is limited to only one class and/or sanctioning body.

Putting a 47/88 in the stock location and orientation requires some custom work anyway.....since all that has to be done I'd like to see them do away with the location rules so people could put them where they want. There are some weight penalties in TSO for liquid i/c and a few other items.....I haven't looked at them in a while. It may be possible to compete in TSO with a totally custom set-up. I guess I'd look into the rules if I were serious. The location rule may be a BG only issue because they want cookie cutter in BG. I guess a Buick running 8.0's is more impressive with a stock location 88mm turbo than it is with an 88mm in the grille

 

[Louie L.]

John Kolivas posted the most useful data on the front facing turbo debate on Yellowbullet. He tested the same turbo, the same day on the same car turbos in both positions. There was a considerable drop in back pressure.

 

[notacarlo]

a simple answer would be that our cars were designed with turbochargers. These race cars had to have them added, so space is a factor. With a little V6, we could virtually put them anywhere we wanted.

 

[Bent6]

Putting a 47/88 in the stock location and orientation requires some custom work anyway.....since all that has to be done I'd like to see them do away with the location rules so people could put them where they want. There are some weight penalties in TSO for liquid i/c and a few other items.....I haven't looked at them in a while. It may be possible to compete in TSO with a totally custom set-up. I guess I'd look into the rules if I were serious. The location rule may be a BG only issue because they want cookie cutter in BG. I guess a Buick running 8.0's is more impressive with a stock location 88mm turbo than it is with an 88mm in the grille

Looks like we got a little off topic here but...............

I agree with you - especially since there's custom fab work involved either way. I've always wanted to do one stuck in the grill with twin mini radiators off to the sides. The current TSO rules I've looked at all still require the turbo to be in the stock orientation with the GSCA rules even more restrictive saying it has to be within 2" of the stock location! The rear framerail thing is just me - IMO cars look better when they can be built around the tire instead of the tire being crammed into whatever space is available. I think the class could grow and enable the Buicks to showcase what we've can do in other arenas if the rules were rethought a little. My current ride is plenty fast but not fast enough for the big tire Pro-Outlaw stuff and doesn't fit other class rules due to the tube chassis, tire size, V6, etc. etc. I just want to build a car that is versatile and could go class racing. Just my .02 but I don't think that counts much if you don't currently run the class.

 

[JDEstill]

I've always thought the forward facing turbo is the best orientation. What's been posted about real world experience jives with what I think should happen theoretically.

Two gains that come to mind with a forward facing turbo, both as a result of improving pressure ratios. Both turbines and compressors deal with pressure ratios (ie P2/P1). This is outlet pressure/inlet pressure for compressors and inlet pressure/outlet pressure for turbines. You see this on compressor curves, where they don't list the boost pressure, they give the pressure ratio, because that is what is actually important.

Gain #1. Eliminate the big elbow on the turbine outlet (ie downpipe). A straight shot out of the turbine should be a big help, just like other exhaust modifications. This falls into the same category as getting rid of the cat converter, eliminating restrictive mufflers, installing a bigger downpipe, adding better flowing pipes, etc. All of these changes decrease the pressure at the turbine outlet (ie there is less restriction from the turbine outlet to the tip of the tail pipe. Since the pressure at the tail pipe outlet is fixed, it is atmospheric pressure, that means the pressure at the turbine outlet *must* be less.)

The turbine provides power to the compressor side of the turbo, and some given pressure ratio is required to provide that amount of power. If you decrease the turbine outlet pressure, then a lower turbine inlet pressure (ie exhaust backpressure) results, while keeping the same pressure ratio and therefore the same power delivery.

For example - suppose the turbine needs a pressure ratio of 2.5 to provide the power needed by the compressor for the boost and air flow desired. If the pressure at the turbine outlet is 7 psig, then the turbine inlet pressure must be 2.5 x 7 = 17.5 psig. Now we do something to reduce the pressure at the turbine outlet (eliminate the big elbow, no cat conv, install a 3" downpipe, etc) and the new pressure there is 5 psig. The new inlet pressure, still at the same pressure ratio as before, is 2.5 x 5 = 12.5 psig. A 5 psig drop in exhaust backpressure thanks to the 2 psi drop in turbine outlet pressure! And as we all know, lower backpressure means more airflow into the engine, and therefore more power.

I think this was one of the causes of the big gains seen on Project X oh so many years ago, that set up had the turbos mounted in a forward facing manner.

Gain #2 - with the setup shown for the race cars, with the compressor suction sticking out through the grill or bumper, there is again a gain due to pressure ratio. In this case eliminating any suction side restriction (air filter, piping, MAF sensor, etc), will increase the suction pressure seen by the compressor. For a given boost level then the required pressure ratio goes down. In other words, it takes less pressure ratio to make 25 psi boost when the suction is open to the outside air than when the compressor is sucking through a MAF sensor, MAF pipe, air filter, etc. And a long MAF pipe with bends just makes that worse. A lower pressure ratio means the compressor takes less power to drive. Less power required by the compressor means less power that has to be provided by the turbine. Less power from the turbine means the back pressure required drops off some. And once again you see more power due to less exhaust backpressure.

So I think the forward facing turbo is the way to go. I would love to do that to my car, but as has been noted previously, I like bolt on solutions Maybe someone should make a prototype and see what the power gains are, then sell a kit. What would we need... a passenger side header with the turbo flange reclocked. A new downpipe. A new compressor outlet pipe with an elbow to connect to the intercooler. And some arrangement for the air filter and MAF. Probably cost prohibitive for all that, unless the power gain was unreal. But if you are building a car from scratch, and you have to build such things no matter what, it makes sense to arrange everything that way. At least it does to me. I've toyed with the idea of a turbo 6 powered kit car, and if I ever do it, I'll be using a forward facing turbo arrangement.

John

 

[driven87]

Now the question is would a 6" necked down to 4" almost straight shot pipe to the current turbo location work a little bit like being in front?

 

[Dusty Bradford]

Now the question is would a 6" necked down to 4" almost straight shot pipe to the current turbo location work a little bit like being in front?

It could help. You'd have to get the fresh air from a high pressure area on the front of the car.

This is the same thing guys like Fiscus, Gomes and Cruz have done with their TSO combo's. Since the rules require the turbo to be in the stock location they feed the turbo with a 5" pipe routed from the air dam.

 

[Dusty Bradford]

So I think the forward facing turbo is the way to go. I would love to do that to my car, but as has been noted previously, I like bolt on solutions Maybe someone should make a prototype and see what the power gains are, then sell a kit. What would we need... a passenger side header with the turbo flange reclocked. A new downpipe. A new compressor outlet pipe with an elbow to connect to the intercooler. And some arrangement for the air filter and MAF. Probably cost prohibitive for all that, unless the power gain was unreal. But if you are building a car from scratch, and you have to build such things no matter what, it makes sense to arrange everything that way. At least it does to me. I've toyed with the idea of a turbo 6 powered kit car, and if I ever do it, I'll be using a forward facing turbo arrangement.

John

When having to run the filter and stock MAF, I'd bet there isn't much to gain. To see the largest gain you would want the turbo pulling air from the headlight area because you still have a radiator in the way of the grill and you would not want an air filter or MAF to get in the way.

 

[Nick Micale]

I was wondering on another race site and there was a post with pics from a track event and there was alot of turbo cars. I noticed just about all the turbo cars has the turbo facing the front of the car and had a hole in the bumper with a large pipe feeding the turbo.....

I am glad someone finally brought this up here!

About 8 months ago when building an 8 sec. GN I decided we would rotate the turbo to face front. This simplified so many items like air intake around the distributor, downpipe design, support bracing for the turbo and others.

Since this was a custom installation, I have since decided to do a header that will rotate the turbo in a regular GN. Most of the parts are in house for this project, and the fixture is almost completed.

There are other items to address that must be considered when doing this on a stock GN.

First, to oil drain must terminate at the oil pan or somewhere lower than the stock drain hole in the block.

Second, a bracket for additional support for the turbo must be provided to remove bending stress on the header. We have designed a bracket that will bolt to the front of the pass head to accomplish this.

Also, the pipe to the intercooler from the turbo must also be modified. When doing this change, we weld a flange to the compressor outlet and the pipe, and join them with a band clamp. In my case we will also modify the throttle body by welding a flange on it to mate with one welded on the up pipe.

Our current plan is to have the pre-production set on a running car in about a month.