At 10 lbs of boost backpressure just above the hot inlet is 44 lbs. I am going to pull the turbos and send them to a Garrett distributor.

 

Sean is talking about the ratio across the turbine and you are talking about intake versus exhaust. Two different measurements. Sean works for Garrett and is trying to help point you in the right direction.

Regardless, the measurement that you've been taking should be closer to 2:1 in performance applications. (Closer to 1:1 for stock turbo cars at stock boost level) It sounds like Sean is suggesting that you may have an exhaust housing or turbine wheel that is not a proper match for the engine and flow rate you're trying to run at. I would tend to agree since you have 44psi between the engine and turbine.

That much backpressure also means that you're likely to not be able to run the right amount of spark advance without getting knock. Freeing up the turbine flow with a proper size matching should reduce backpressure and allow you to advance the timing a bit. Both of these will improve your power output.

 

I appreciate all the help I've gotten. I have not pulled the turbos yet. We have to drop the engine to do so. We have wondered about having a real one off turbo for some time and have considered a mismatched wheel. I'll have them make the measurements once the turbos are pulled next week.

Thanks to all.

 

Let us know what you find.

BTW, it's possible you could also be running into compressor choke so make sure you get measurements on both ends.

 

The turbos have been identified as one off. I have GT35Rs per Lingenfelter. However the exhaust housing is a T25 with internal wastegates. Generally GT35s come with a T3 flange. I'm pretty stuck with the turbos as I have no room for external wastegates so I can't readily change to a T3 housing. At least the T25 has a .82 A/R.

As I stated we removed the third intercooler and gained 1000rpms and 100 HP at 10psi. We measured the drop in pressure across the other two intercoolers and we're getting 4-5psi drop at differing boost levels. So we will be replacing them with either two custom made duplicate but more efficient ones or most likely going to one larger front mount intercooler.

A&A has a 3.5x6x26inch intercooler they state has a drop of 1/2psi although they state they've never measured the pressure drop across the intercooler. I have room for just a slightly larger intercooler at 4x6x26. Has anyone measured the drop across Andy's intercooler.

I'm relatively certain I can gain another 100+HP and enough RPMs to get to 6800 to reach my goals. I bemoaned my present turbos at first but if I can get to 800 then actually I'll have quicker and more power down low with the present exhaust housings. I don't plan to run a Texas mile so I'm going to stick with the present turbos as is assuming my intercooler change gets me to my goals.

Thanks for all the great help from everyone. I'll report back with the next dyno. I expect it will be two weeks before we're ready to run one again. Thanks again.

 

I've never run a pressure check across the core, but I can tell you that the most respected intercooler design and fabrication company in the country was involved in the design and construction of this unit. I can't imagine you'll come anywhere close to your current pressure drop across one of Andy's

 

Thanks. We'll check the drop before installing but I'll be surprised if its more than 1lb. They also have the fittings already made for installation which will save me time and money. All I'll have to do is make pipes from the turbos to the intercooler.

 

An update. Put in a treadstone single front mounted intercooler and rerouted all the plumbing. Tossed the non-hard tubing from the turbos to the intercooler and raised them up to avoid hitting the wheels using stainless steel. Had a spoiler made to route air to the intercooler and radiator. Had a shroud made as well.

No dyno yet though. He sent some pics but they aren't very good so I'm not posting them. Should have a 1-1.5lb drop across this intercooler so I'm hoping I've removed enough backpressure to meet my goals of 800 hp.

Can't wait until I get the bill for all of it.

 

Everything but the radiator shroud is installed regarding the new intercooler and plumbing. It supposedly will be ready next week. The air inlets for the old small intercoolers are being plugged with metal plates to keep water from the new air filters.

The transbrace from ECS is loosely installed. The new Eaton carrier will be installed after the dyno.

The dyno is being planned for the end of next week. Hopefully I'll gain the rest of my RPMs and be rid of enough backpressure to meet my goals. We'll see. Oh, we installed the new hardened shafts from ECS that came with the Eaton carrier. I hope the new but stock couplers will hold up to the new power. I'm second guessing myself about those and the stock crank now.