I was looking at this setup: Turbonetics 62-1 compressor .70A/R exhaust P-trim .96A/R tang/divided with ceramic BB option, custom(stainless) manifold with divided/equal length runners, HKS racing wastegate, custom(stainless) DP. What are your opinions on this setup? I'm planning on runing 18psi daily and maybe 20psi with race fuel. I'd like to see 400-450rwhp at 18psi if possible.

 

I'll be the first admit that I don't have a single yet, but I have been asking lots of questions to RX-7 guys and turbo people in general, so here is what I think.

You sound like you are well on your way to a good setup. Your turbo sizing looks good. The only area I would debate would be the exhaust AR. I might be tempted to up it one or two sizes. The BB option lets you run one larger size AR without increasing lag. So I would think at least one size bigger if not two increases because of the HP you are trying to get. If you can't get the air out of the engine because of too small of an AR, then the engine will choke at high rpm because of the backpressure.

 

I'd also go with a TIAL 40mm wastegate, simply because they make some REALLY nice hardware, and you'll need a good wastegate so that your car doesn't, as Spyfish said, choke on its own exhaust. TIAL sells the same wastegates it makes for CART cars, by the way.

 

I think it depends on how your motor is ported. but I have seen a car with the same spec turbo run 475 to the wheels on that boost. .96 is pretty big, and I really dont think you will choke the motor unless you are trying to go over 8500rpm.

everyone wants to run such high boost. I would rather make more power on less boost. I guess i will find out soon when my car is back together.

 

I second the Tial wastegate and sizing the turbo to run on less boost.

 

.96 on a to4 turbo is small....

I run a to4 with a 1.32 rear housing and it is excellent, it does not make full boost (on data logger) till around 7200 to 7600 rpm, however on the boost gauge it shows "full" by around 6000rpm, my peak power happens at around 8200rpm. I have a real strong flat torque curve "linear power" over a rpm range from 5500rpm to 8500rpm, which is a perfect match for the gear ratio's of the std box and results in excellent accelearation when engine is kept in this rev range.

This is the way to make "high" power with LOW boost, it is an easy equation greater VE% happens when there is least back pressure on the engine (eg largest rear housing, tolerable or very big wastegate system).

I use a 1.32 rear housing and a 45 mm HKS gate and make between 490 to 520 bhp (depending on ambient conditions) with 14.5 psi/1bar boost with a street ported engine with race exhaust ports.

 

I was thinking of going with a A/R of 1.0 or 1.15, but I thought that might be too much for the porting that was done to my engine which is by no means "big". I think they're pretty much normal for a standard "street" port, and maybe even a little on the conservative side. As for the WG, isn't the HKS racing 50mm? If so wouldn't that be better than the Tial 40mm? Btw where can I get some more info on the Tial? I really don't want to make most power up around 8K-9K rpm so I don't think I need that big of an exhaust housing.
Rice Racing,
You make full boost at 7200 rpm?? Isn't that a little too high? I definitely don't want something like that. Then again maybe your setup is done purposely that way.
Thanks for all the input.

 

When my porting was less, my max boost was at 6700rpm with the 1.32 rear housing....However the power peak was at about 7500rpm and the power band was about the same and lower down. The power was less due to the lower revs.

I would say that if you want say max boost "ie max torque" at the 5000 to 6000 rpm range, go with the 1.15 or .96 housing...I always tend to go for the larger one

The valve in the HKS gate measure 50mm but the opening in the body ENTRY is 45mm...the outlet is a bit larger (around 50mm)

 

Hey if you guys need Tial Wastegates let me know because my friend is the East Coast Dist.. (TNT Motorsports in New York)
Tial has a 40mm & 46mm right now and will have a 60mm available in a couple of weeks... IMO Tial wastegates are of the highest quality... Email me for more info and pricing. Enzo250@hotmail.com

 

Hey Mach2:

Go with a Turbonetics 62-1, .7 comp housing, P-Trim w/ 1.15 Tang/divided. The power will come on strong at 4000k all the way to 9000k+
As for the wastegate a Tial 46mm will outflow a Hks 50mm, Plus the Tial's lower section and seat is stainless compared to cast iron and mild steel on the hks.

You should easily get 450rwhp with this turbo...

 

RICERACING: Full boost by 7200 rpm with a 1.32 A/R ??? damn, I can't wait that long !!!

I know you guys like big A/Rs....but for most guys here they don't plan on spinning the engine past 8-8.5krpm, therefore .96 AR undivided or 1.00 A/R divided is good. And like someone mentioned, if running the BB option then you could afford to run one size up.

I've dynoed my car with both a .81 A/R and a .96 A/R P-trim mated to a T-70 and the only major difference was that both HP/TQ curve started 500 rpm earlier with the .81 A/R and HP peaked out @ 7.5 krpm vs 7.7-7.8krpm for the .96 A/R. Peak HP between each was less then 10 RWH but I gained alot more from 4.5-5krpm.
Torque is flat from 4.5-5krpm til 7.5krpm !!

Simply my experiece....

John D

 

One way to help sizing your A/R could be done by measuring the TIP or turbine inlet pressure... There's a ratio between your intake pressure(boost) and TIP......which I forgot... damn
Anybody know it ????

Hey Rice Racing, when your full boost hits it must feel like you were hit by a train from behind !!!

Big A/R's will make tons of hp when high rpm motors are used....look at Toyota 2.1 4 banger used in the Pikes peak in the Tacoma or Celica making 900+ HP !!!

Later,
John

 

John

Yeah my torque is not totaly flat,at 4k it will only make 10psi (0.7bar boost) it is a steady linear rise "realy" starts from 5k (0.83bar boost) and peaks at 7200 to 7600 rpm (1bar boost) and my peak power happens at around 8200 to 8400 rpm. My porting has a bit to do with this as well. Basically from 5k onwards I have over 90% of whatever my max boost setting is which is ideal for me and the way I like the power delivery. (It will pull to 8800rpm in top gear) Over 200mph !

There is a noticable power peak and you can realy feel the extra power once past 7000rpm but it by no means is a light switch type of feeling (on or off) it is just realy biased towards the top end, hence I do not have a very flat torque peak like yours.

I just was trying to aim for the most amount of power I could make at 1bar and as at high revs as possible to reduce combustion pressure stress on the engine with out resorting to a bridge or peripheral intake.

Did not want it to make max power at over 8500rpm though, cause this would mean that I would have to rev it over 9k to get max use of the power band. At present I change at 8500rpm...cause I have race clearancing of the rotors I sometimes extend the changes to 8800rpm

RPM drops: when changing up from 1st through 5th

8500 rpm 4920 rpm 2nd
8500 rpm 5868 rpm 3rd
8500 rpm 6110 rpm 4th
8500 rpm 6477 rpm 5th

Suits my power band spot on, first to second is not realy an issue cause I cannot use all the "torque" POWER available anyway, I always end up pedaling the car, in these lower gears...basically I have the power where I need it.

 

Cool !!!

When drag racing the ideal is to attemp making the most power (average) in the rpm range where motor will operate during gear shifts like Riceracing expalined.

 

So what A/R would you recommend for road course racing? I'm looking at a 60-1, p-trim, 0.96 or 0.81 a/r.

"Peak HP between each was less then 10 RWH but I gained alot more from 4.5-5krpm.
Torque is flat from 4.5-5krpm til 7.5krpm !! "

John, are you saying the 0.96 or the 0.81 gave you more/flatter torque?

 

Bump.....anyone listening?