5.73@122.1 DRW/Buick new best.

[Alky V6]

If you're familiar with both, I'd like a suggestion for each. I'm sure you're familiar with the GT4788. Do you have any experience with the S480?

 

[Alky V6]

Oh Norb, the ambient temps were not extreme if I remember correctly. Mid 70s.

 

[John Wilde]

If you're familiar with both, I'd like a suggestion for each. I'm sure you're familiar with the GT4788. Do you have any experience with the S480?

I don't but Dusty does, a friend of his has one on a V8.
You may want to hit up Jose at forecedinductions on the BW stuff.
He seems to be the most knowledgeable person I know of with them.

 

[Alky V6]

Thanks John. I value your opinions very much.

 

[John Wilde]

Thanks John. I value your opinions very much.

Thanks man, my wife loves San Diego, want to give me a job?

 

[Alky V6]

Hey, if I had enough work flow for ya, it wouldn't be a problem. You're hired.

 

[lazaris]

Don the issue you talked about with the adjustment on the gate is showing that the BP is causing it to push open. As far as a T-6 or T-4 I believe Ted is still using a T-4 on his 47-88. Hes well in the mid 8's. I think you can go pretty far on a T-4 with a 224 cu in's with the right turbine wheel and exh housing. Thats why a BP reading would really help you.

 

[Cheeseburger]

Very immpressive, always like watching your car videos too!

 

[John Wilde]

Don the issue you talked about with the adjustment on the gate is showing that the BP is causing it to push open. As far as a T-6 or T-4 I believe Ted is still using a T-4 on his 47-88. Hes well in the mid 8's. I think you can go pretty far on a T-4 with a 224 cu in's with the right turbine wheel and exh housing. Thats why a BP reading would really help you.

Ted is not running a alky motor it is not a fair comparison.
Alky turbo motors need much more breathing on the turbine side.
Ask Garrett, Precision, Turbonetics or any of the companies supporting
alky drag cars. For Don's application there is no downside for a T6 Flange.
However this does not mean it would not work with a BIG T4.

 

[John Wilde]

BTW: My response sounds jerky, but it is not meant to be. Sorry Laz...
The flu and ear infection are killing me.

 

[Alky V6]

I really appreciate the feedback on this. All points are valid. I'm pumped up now. I'll get that back pressure reading first before I do anything else. That should be on the 22nd or earlier if something is going on at Barona before then. Thanks again, everyone.

 

[lazaris]

BTW: My response sounds jerky, but it is not meant to be. Sorry Laz...
The flu and ear infection are killing me.

Not taken as jerky. I'll also point out that Ted's car has about 50 more cubic inches on Don's. This in itself requires more exhaust flow as compared to the smaller motor. So you must take this into consideration as well. I'm sure either Flange can be made to work. The T-4 will just incur less work for Don.

 

[Alky V6]

Very immpressive, always like watching your car videos too!

Thanks Cheeseburger. It's always nice to know the effort's are being enjoyed by others.

 

[bison]

My guess on the backpressure is 48psig at 32 psig intake pressure. Id run the t6 flange with as big an a/r as you can stand. Just increase the N2O on spoolup to take care of the spool. If you go really large ont he compressor you may need to change cams but the head flow will be choking you for sure if you did that. Id just look for more exhaust wheel and housing flow. There is probably 80-100hp in just that.We will see after you post the bp number. Your mph should shoot up a lot. That old 76Q is being worked pretty hard.

 

[Alky V6]

Remember, I'm not even using the max (29.9 psi) spring package in the wastegate AND it's cracking open. To me that makes me think it's a relatively lower bp. It's fun guessing on this.

Bison, I appreciate the advice. I'm already using a pretty big shhtick in the motor. A lot bigger than everyone would think is needed. I originally spec'ed the cam to make up for the deficiencies of the heads and make the most of them as they were. Granted, the target hp level back at the beginning was around 800 hp, not 935, and certainly not 1234. Gosh, I'm still running the original 1.835 int. and 1.5 exh. valve sizes.

I calculate I'm pumping about 84 lb/min airflow. Real close to the limit for the T76, but not quite over it. For those getting their calculators out, that's 11.1 hp per lb/min airflow. I'm getting about 10% more hp for each lb/min airflow because of the methanol.

I can verify that the engine simulation software I use has been right on, up to this point.

 

[Alky V6]

I've been playing with the turbine housing a/r size on the engine simulator. Don't have a T6 housing to measure, so I'm guesstimating that the radius dimension for the a/r calculation is 4.79". There is a much larger nozzle size difference from one a/r size to the next with the larger T6 housing radius.
This is what I came up with:
.96 a/r = 2.42" nozzle diameter.
1.08 = 2.57".
1.23 = 2.74".
1.39 = 2.91".

When I plug in the .96 a/r, full boost (45 psi) by 6000 rpm.
With the 1.08 a/r, full boost by 6500 rpm with a slight reduction in the maximum level of boost, causing a drop of around 45hp. A drop in turbo shaft speed is responsible for this.
With the 1.23 a/r, the boost level never attained even 10 psi up to 7800 rpm.
Didn't even try the 1.39.
The simulator showed a maximum hp level when using 2.5" for the nozzle diameter.

Does anyone have a T6 housing they could work with me to get a truer radius dimension? Pwease? :tongue: Talking about a Garret housing.

 

[bison]

Remember, I'm not even using the max (29.9 psi) spring package in the wastegate AND it's cracking open. To me that makes me think it's a relatively lower bp. It's fun guessing on this.

Bison, I appreciate the advice. I'm already using a pretty big shhtick in the motor. A lot bigger than everyone would think is needed. I originally spec'ed the cam to make up for the deficiencies of the heads and make the most of them as they were. Granted, the target hp level back at the beginning was around 800 hp, not 935, and certainly not 1234. Gosh, I'm still running the original 1.835 int. and 1.5 exh. valve sizes.

I calculate I'm pumping about 84 lb/min airflow. Real close to the limit for the T76, but not quite over it. For those getting their calculators out, that's 11.1 hp per lb/min airflow. I'm getting about 10% more hp for each lb/min airflow because of the methanol.

I can verify that the engine simulation software I use has been right on, up to this point.

I agree with the bp prediction slightly. One thing that will happen is as soon as the gate does crack under the pressure it will be limited to what it was just before it cracked for the most part. You really need to hold the gate shut and use an electronic controller to see the actual bp. It should climb rapidly as it spools and then taper off a little and climb up as the engine speed increases. Once the turbine shaft speed is reached it doesnt take anywhere near as much energy to keep it going as it did to get it spooled though it will still continue to increase as the engine speed increases.

 

[bison]

I've been playing with the turbine housing a/r size on the engine simulator. Don't have a T6 housing to measure, so I'm guesstimating that the radius dimension for the a/r calculation is 4.79". There is a much larger nozzle size difference from one a/r size to the next with the larger T6 housing radius.
This is what I came up with:
.96 a/r = 2.42" nozzle diameter.
1.08 = 2.57".
1.23 = 2.74".
1.39 = 2.91".

When I plug in the .96 a/r, full boost (45 psi) by 6000 rpm.
With the 1.08 a/r, full boost by 6500 rpm with a slight reduction in the maximum level of boost, causing a drop of around 45hp. A drop in turbo shaft speed is responsible for this.
With the 1.23 a/r, the boost level never attained even 10 psi up to 7800 rpm.
Didn't even try the 1.39.
The simulator showed a maximum hp level when using 2.5" for the nozzle diameter.

Does anyone have a T6 housing they could work with me to get a truer radius dimension? Pwease? :tongue: Talking about a Garret housing.

I dont think the simulator is accurate when using the N2O to spool. Like i stated earlier it takes a lot more energy (which the N2O is providing a lot of from all the oxygen) to get the shaft speed up than it does to maintain it. Id think you could spool almost anything with the N2O.

 

[Alky V6]

I agree with the bp prediction slightly. One thing that will happen is as soon as the gate does crack under the pressure it will be limited to what it was just before it cracked for the most part. You really need to hold the gate shut and use an electronic controller to see the actual bp. It should climb rapidly as it spools and then taper off a little and climb up as the engine speed increases. Once the turbine shaft speed is reached it doesnt take anywhere near as much energy to keep it going as it did to get it spooled though it will still continue to increase as the engine speed increases.

I think I understand what you're talking about. What I've noticed as I've been stepping up the spring package and the boost level, is the boost would climb steeper with each increase of the spring preload. With the lighter spring packages the boost ramp up would have a large roll over as it approached the boost level set by the controller. I am using an electronic controller on the wastegate, with manifold pressure for control pressure. As the springs were made stiffer, the ramp up would get steeper and the point at which the boost level was reached would get sharper with less of a roll over into max boost, but with no over spiking. Once I felt comfortable with the ramp up rate of the boost, I started to up the boost level, starting at 26 psi. As I started going over 28 psi, I started seeing the boost dropping with engine rpm. I would reach max boost by 6200 rpm, then the boost would drop to 28 by the shift point (7,400). After the shift, the boost was back up and it would drop again until the next shift. Then the same pattern again all the way to the finish line. The last try at cranking the wastegate spring tension up resulted in the tires blowing away on the 1-2 shift. I backed it back down, and that's where it is now.

I'm assuming that with the electronic controller, if the turbo capacity was there, the boost level should stay flat as rpm increased. Plus, this turbo doesn't have the slightest hint of wanting to spike over the high target boost level, which is something else that tells me, this turbo is over. I have the electronic boost controller set to not provide any ramping effects on the boost rise.

 

[Alky V6]

I dont think the simulator is accurate when using the N2O to spool. Like i stated earlier it takes a lot more energy (which the N2O is providing a lot of from all the oxygen) to get the shaft speed up than it does to maintain it. Id think you could spool almost anything with the N2O.

Yeah, I don't think there would be any problem getting the turbo to 16 psi. It's after the nitrous shuts down at 16 psi that I'm worried about. Would there be enough exhaust energy at that point to continue a decent boost rise rate up to max boost level???

With the present setup, you can notice a slight drop off in power when the nitrous turns off and before the turbo picks it back up. If the boost rise rate is slow after the nitrous shuts down with the larger turbine housing, it could be unexceptable. In fact, I simulated the nitrous shot at the beginning of the run, which shut down .8 seconds into the run and the boost level dropped and stayed low for quite some time. A drop from 1200hp to 400hp after the nitrous shut down. That was with the 1.08 housing. When I went back to the .96, no problem. Not to say this would definitely happen, but it makes you think about it a little.