Rogue Status

iTrader: (1)

So I am still up in the air as to what I want to do with my swapped wagon. Car is an '81 Volvo 245 with a LM7/T56 combo swapped in. I have been driving the car for almost 2 years since the swap with no major issues aside from a lack of POWER!

Prior to building the Volvo, I had started a build on a 2nd gen RX-7 that had the same engine and trans with a 76mm On3 turbo. I fabricated the crossover and the goal was 650whp+

I sold the turbo stuffs to fund the swap and haven't looked back. Now I am wanting add some much needed horsepower to the wagon as I have finally sorted out the majority of the chassis and will soon add 13" front brakes, power steering, and some beefier bushings for the rear axle.

IMO the biggest challenge I am facing is rear tire. The absolute widest tire I can stuff back there is a 255 without body work that I really don't want to do as the car has been so well preserved for the past 30+ years. I am going to cap whp at 500 with a turbo setup. I feel like any more is going to be pointless and just destroy tires rather than egos. The other option is to add a cam and build it for N/A power. I could squeeze close to 350whp out of the little 5.3 with a cam and some other nic nacs. At the end of the day, I think I just miss boost from when I had my 1.8T GTi with 350whp. That thing was a blast, the little T3/T4 50 Trim climbed from 12 psi to 25 psi in a snap and hit super hard.

So onto the question now that I have tried to explain my relatively mediocre power goals.

What budget turbo would you recommend to make 500whp, eBay GT45, On3 76mm, eBay T76 (76/65), T70/70mm, ect. I am looking for usable power with good street manners with the T56. I don't expect the thing to make full boost off idle, but I don't want to have to wait until 4500rpms to get going.

I specify budget as I am on a tight one with this project and with my power goals, I am sure there is a budget option that will be more than adequate.

I have also searched endlessly for 5.3/T56 turbo information with little to no luck in regards to spool. A few threads were promising, then they swapped in autos. There are countless automatic cars out there for approximate whp numbers, but nothing I have found specifies positive pressure RPM and full spool RPM with a T56.

Thanks in advance everyone, link me to resources if I have overlooked them in my searches.

Pic of the car:

Rise of the Phoenix

iTrader: (27)

That's an interesting car you have there, but very cool. If you goal is 500 rwhp, any of those turbos listed will get you there, and provide quite a bit more if you ever want to up the boost.

SM105K

iTrader: (3)

That thing is awesome, and there is a reason why people swap to autos. Driving a stalled auto with boost is way more fun then banging grears IMO.

Rise of the Phoenix

iTrader: (27)

Maybe if you have a VAGINA!

Rogue Status

iTrader: (1)

It might get the wick turned up if I want to impress on the rollers. On the street, I am sure 500whp will be more than enough to scare me to death and walk 90% of the cars on the road in Charleston. I am confident 500whp on a 245/40 17 is going to be a handful.

Thanks! Car was originally a 4 speed manual, and I want to keep a manual in the car. I don't plan on drag racing, just roll racing from time to time.

Forcefed86

iTrader: (4)

GT45 hands down IMO. It has the best exhaust wheel to comp wheel ratio. Forget which mag. Just did an article… but the 69mm GT45 on a stock 5.3 made more power than the smaller wheel 76/65.

Edit:

Found it...

http://www.gm-efi.com/tech/budget-bo...turbo-testing/

JoeNova

For 500whp I would honestly go with the 7665. Mainly because your car is a manual and it'll spool much quicker. Unless you're planning on maxing them out, you won't tell much of a different power wise.

I've seen a few people hit 650whp with a 5.3 and the 7665 lately. But with that turbine, keep the cam small. Like a stock LS1 or maybe LS6 cam small. If it was an Auto, the GT45 would get my vote.


That magazine article wasn't exactly the best comparison, either.
They used a fairly large cam, which put the turbine on the 76mm at a huge disadvantage. Not only is the wheel smaller, it also has a much smaller A/R as well. A better comparison would have been a stock cam.

Forcefed86

iTrader: (4)

Good points! That article was pretty lame. I didn’t even see them mention the exh wheel size’s or the AR sizes? Or the GT45’s compressor size?

It seems the longer I play with this stuff that the turbine wheel is more critical than the compressor when you get into similar turbos and power production. A 69-70mm comp wheel is more than capable of his goals. Once you factor in the leverage with the gt45’s 77mm exh wheel over the 65mm p-trim stuff, I’d have to put my money on the gt45 for best response time as well. (even with a OEM cam) When compared to the 76/65 turbos with similar AR housings anyway. Could be wrong… would be a cool test.

For 500whp peak goal he could probably go with a 66/65 on3 unit... I'm told they stock these you just need to call and ask.

JoeNova

The CXRacing 76mm is standard with a .68 A/R turbine on the 65mm wheel. I think you Can opt into an .82 or .96. They mentioned the .96 A/R in the article. The GT45 has a 77mm turbine wheel with a 1.05 or 1.10 A/R depending on who you get it from.

All other variables aside, the turbine on the 76mm didn't stand a chance with the 224/232 115 LSA cam they put on the 4.8. The turbine was already being choked at 4500 RPM on the 76mm to the point where boost started to drop off from 6.5 PSI to 5.5 PSI by red-line. The 76mm works very well on smaller engines or V8s with very small camshafts. Beyond that, it has a lot of trouble keeping up. This is why a few guys here topped them out at 11 or so PSI on a cam/heads LS1 at 550 whp, but stock or small cam 4.8/5.3 guys have made 650 (or sometimes more) with them.

OP, Moral of the story? They're not all the same. Pick the one best suited for you.

Rogue Status

iTrader: (1)

Awesome information everyone. I was all set on the GT45 but didn't want to count out the 76mm or 70mm guys. I think having the GT45 spool a touch later than the 76mm or 70mm might help with traction in lower gears. There is a YouTube vid of a guy that has posted on ls1Tech with a '65 Mustang, GT45 on a 5.3 w/ T56. At 7psi it seems to hook just fine, 16psi is a different story. From what I can tell we should have similar tire sizes. The car seemed plenty fast at 7psi.

Ultimately I think 7-10psi for everyday bumping around town and get it tuned for more if I ever need it. My GTi had a on/off solenoid to run WG pressure (12psi) and MBC pressure (25psi). I could flip the switch mid pull if I needed to. The turbo was a touch slower to respond, but it worked. I think a V8 application boost delivery is going to be much different than what I am used to on 4cyl engines.

Tjabo

In addition to all of the other problems with that article that frustrate me a bit, does anyone think those numbers are awfully high? 650bhp is about 550whp in a manual transmission car, right? On 7psi???

Looks like maybe I need to stick with the GT45 instead of moving toward the new On3 76mm I just got. Lol

I just wish they would have at least equalized the boost levels...

coltboostin

This guy gets it!!

JoeNova

Engine dyno numbers with no accessories, a large cam, and an electric water pump. With that cam they wouldn't have gotten too far before power started to fall off. Hell, the 65mm turbine was already stressing the 6 PSI. That's probably why they kept boost numbers low for the comparison.

Rogue Status

iTrader: (1)

Bumping this back up. Any real world numbers in regards to spool with a T56, 5.3 and any of the above turbos?

Rogue Status

iTrader: (1)

Anyone? There has to be someone running around with a Turbo 5.3 and a T56.

Tjabo

A slightly off topic bump for this thread to keep it alive for pertinent results maybe:

Here's what I just don't quite understand, if the wastegates are providing enough passby of the exhaust gasses to keep the turbine and compressor wheels at the speed they need to be to pump the required air for a given boost level, how does the turbine "choke up?" If the turbine really is choking, it seems to me like boost creep would be the natural result..... Especially at these low boost levels!

BTW, I have the normal eBay gt45 (DNA Motoring?) and the On3 7665 (.96?) on the shelf. They both seem super nice in terms of build quality. The On3 is tiny by physical comparison, and I think it's about 17# lighter IIRC from when I weighed them.

1320king

iTrader: (4)

what about the on3 78?

Rogue Status

iTrader: (1)

I have considered that turbo as well. I don't think it is necessary with my power goals, but would be an option.

I think the GT45 is going to be the way to go. A 2" crossover should help spool and cam would work wonders. I was hoping to catch the attention of Jon Volk, he posted his Mustang in here a while ago. 5.3, GT45, T56, crossover like I plan on building and a full exhaust. In his YouTube vids car looks quick at 7psi and a tire slaying monster at 15psi. Spool seems reasonable but just wanted to get a grasp on RPM.

1320king

iTrader: (4)

Jon is an awesome guy. His shop is like 30 mins from me. I can text him and inform him of the thread and see if he can chime in.

Forcefed86

iTrader: (4)

Nice size comparison... ON3 VS GT45.