I’ve done quite a bit of searching and most info is 10+ years old. Currently running twin 70mm On3 turbos and I’m suspecting that they may not be very efficient on my setup (backpressure). Looking at precisions, but not sure on the sizing. Spool timing isn’t a huge deal since it’s a 6 speed auto trans. I street drive and drag it.

Specs:
Full weight Fox coupe ~3500 w/out driver
408w 8.5:1 comp on 93 octane 18psi
A-W intercooled
Afr 205 heads, 525 lift cam 230 dur at .050
6200rpm shift point
6r80 trans with a stock convertor
3.25 rear
Full 3” exhaust to a straight through muffler
80lb injectors, 58psi base, twin 465lph

Best so far was 106mph in the 1/8 and 135mph in the quarter. Injector duty is in the 90s. IAT goes up to 160 on the back half, pulling timing to 12.5 total. Without pulling due to IAT 15deg all in at 18psi. Looks to be about 600-650 wheel, which feels about 100hp light at that boost level from what I expected. Are these 70s choking it out that much? What should I switch to?

 

What's your drive pressure (backpressure)? What's the turbine size/ housing? The hot side is more important than the compressor side.

Based on numbers you provided, your a2w system isn't up to par. 160° is hot for 18psi and water cooled. Are you running the water through a heat exchanger, or just using ice water?

 

Compressor 70
Turbine 64.5 .96AR T4
These on3 s are a very old design.

Frozen boost 15x6x6.5” intercooler
Frozen boost 26x7x2 exchanger
85 ambient: Temps start at 120, dip to 110 at the 1/8 then up to 160 by the 1/4
Craig Davies 9gpm pump

Unfortunately, don’t have a way to measure backpressure at the moment.

 

9gpm isn't anywhere near enough coolant flow, and your probably not even getting that. Those ratings are unobstructed, where you are pushing water through 2 heat exchangers which restrict flow. Need to be up around 30gpm for an a2w system.

I did some quick math, at 18psi with 85° ambient those turbos are putting out roughly 287°f air. Your water, at best, is 20° warmer than ambient temp, so water is 105°. Assuming 90% efficiency through your a2w cooler, outlet charge temp is 123°. If your water temp comes up to 150°, charge temp gets into the 160s.

I bet if you could find a way to monitor your charge water temp, you'll see it climbs, indicating the pump isn't circulating enough flow. Imagine your engine, doesn't matter the size of the radiator, if the water pump cant circulate enough coolant, it's still going to get hot.

Get that sorted then we can start to look at turbos.

 

I struggled to find a decent pump that would work. If it’s only pushing 4gpm through a 1 gallon exchanger, then in the quarter I’m not exchanging much fluid at all.

Any recommendations on a pump?

 

Most of the cheap units are just bilge pumps.
You can find dedicated ic water pumps but they won't be cheap. I've seen alot of folks use the BMW pump.

Me personally i am looking into the brushless coolant pump used on GM 2.7L engine. If it can keep a 310hp turbod 2.7 cool, it should be more than capable as an a2w coolant pump.

 

I stayed away from bilge pumps since they look to perform poorly with head pressure. Since I’m limited on radiator fitting size, I may need to look at coolant water pump type pumps. Just like you mentioned.

 

What size hoses are you running?

 

From https://www.s197forum.com/threads/the-great-intercooler-water-pump-test.117785/

Lingenfelter – 9.3gpm

Davies Craig EWP150 – 6gpm

Meziere 55gpm – 5.2gpm

Rule 2000 – 5.1gpm

Bosch/GT500 pump - 5.1gpm

Meziere 20gpm – 4.25gpm

It's worth reading that thread though, they picked up 28% flow going to an intercooler with better flow.

The Stewart EMP 25a intercooler pump is pretty highly regarded, buy you are going to need 1" fittings to go with it.

 

Interesting thread, if those 20-55gpm pumps are in the single digits, curious what a 9gpm is actually moving....

 

10an, could go bigger, I’m sure the head loss or quite high. I was shooting for 1 change per 10 seconds. But looks like I need quite a bit more.

when I did the initial research, I found to have an efficient setup you need -12to-16 an lines with a large pump and large exhanger connections. Head pressure is killer on 12v pumps.

when you run to the trunk and back, head loss can be upwards of 15ft or more, which no pumps flow there. So my lines are small, I would benefit from larger lines to reduce headloss and only have the exchangers being the restriction. That being said, 9gpm still won’t be enough.

 

I'm not sure how the little Chinese pumps fair, that set of tests should be more "real world" tests because the pump is actually pushing on something.

FYI, the intercooler system in my mustang never sees ambient temp, being low and close to the asphalt it is 20-30° above ambient any time the sun is shining. Even on the highway temps stay up there. When surface temp is 130 and the intercooler is 6" above it you are going to see more heat. The closer the exchanger is to the asphalt the worse it will be. \

If I was doing it on a budget I would go with a stock pump out of a 2013/14 GT500, or a ZL1. If you have the money to do it big go with the Stewart EMP and 1" fittings everywhere.

The other thing to do with any of these pumps is make sure your wiring is solid. Good quality wiring and relays, proper grounds and make sure your charging system is working properly.

 

The GT500 pump performs a comparable to the one I currently have. It’s also probably good to note that my exhaust header is a few inches from the intercooler, shielding may also help me.

This is what pointed me at the turbos originally. On3 said I’m maxing out the 70s with that size motor and heads. I know that creates heat. Which made me think the more efficient turbos will bring temps down enough for my system to compensate. And also reduce back pressure to pick up more power.

I finished the car 2 years ago and spent enough money to get it running reasonably well. Now I’m trying to eliminate inefficiencies such as the turbos and now looks like the A-W system.

 

I can calculate the airflow speed into the compressor, and that will tell me if your maxed out or not. What's your elevation, and running filters or open turbos?

 

Small K&N cone air filters in the engine bay. Sea level

 

I ran a single BW 72mm,A/A IC with W/M at 22psi on a 351 and didn't see IATs above*145.

Your motor needs a lot more cam IMO.

 

If you are spraying WM before the IAT and also have the A-A, that’s going to make a huge difference. Head flow and cubic inch is going to play a large roll as well. I have a stock longblock 351w that I switched from the on3 70mm to their 7875 and picked up 9mph in the quarter from just the back pressure difference. It’s the turbine side where I’m hitting the restriction as well as poor water flow in the A-W system.

 

What was the BP difference?

I agree,you have IC, pump issues. Have you tried more timing on the 408?

 

I don’t know what the BP difference was, but the 70 had enough that you could feel the car run flat after 4500 rpm.

Timing is set at 15deg at 18psi. I’m street tuned, so I’m not sure how much I can get away with. At the end of the track I’m losing 2 deg due to IAT and may have 1 or 2 degrees of inductive latency. Which puts me at. 10.5 to 12.5 def total in the back half. That being said, 106 in the 1/8 isn’t a lot of power and I have good IATs up to that point.

I figured the car could take more than 15deg at 18 psi with aluminum heads and 8.5:1 comp, but was advised not to go over 15deg by a local tuner on 93 octane.

 

If you're on pump gas then I HIGHLY recommend installing a Safeguard system. This little gizmo will monitor for the slightest amount of knock in each cylinder then pull timing in the cylinder that is knocking until it doesn't hear it...it's extremely sophisticated and has saved my motor multiple times when I was running pump gas/meth inj:

http://www.jandssafeguard.com/

My car is now a flex fuel car so I run E85 most of the time but I still use it to monitor the cylinders just in case something goes wrong.

ks