When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
There hadn’t been much I was able to research about the EFR 8370 turbo to gather expectations outside of what’s on Turblown’s website so I just wanted to share my results so far in case anyone else is looking for info.
This is a stock port, 60,000 mile FD with the following:
EFR 8370 C Type B-2 frame .92 A/R T4 flange w/ Aluminum CHRA
Turbosmart Gen V IWG
Turblown Cast Manifold
Turblown 500hp E85 Fuel kit
Haltech Nexus R3
V-mount Greddy Intercooler
3” Exhaust with resonators and muffler
Unfortunately could not turn boost up any higher because of the exhaust restriction most likely in resonators. At some point this summer I will resolve the issue and hopefully be able to report the numbers for 25 psi.
Last edited by JaredCarpenter; May 1, 2025 at 08:38 AM.
On the way home I also decided to stop guessing the car’s weight and take it to the local CAT scales with a full tank of gas and a couple bags (does not include me).
I have to wonder if numbers between dynos can vary significantly. And if slapping on top equipment (e.g., ECU) really necessary to make top hp..
Here's an S5 (not my car, that's what I have), street ported (likely stilll flows less that a stock FD), similar size turbo (single scroll) controlled by an Rtek through the stock s4 afm and stock map sensor that made over 425 whp @ 17psi boost!
I have to wonder if numbers between dynos can vary significantly. And if slapping on top equipment (e.g., ECU) really necessary to make top hp..
Here's an S5 (not my car, that's what I have), street ported (likely stilll flows less that a stock FD), similar size turbo (single scroll) controlled by an Rtek through the stock s4 afm and stock map sensor that made over 425 whp @ 17psi boost!
This particular Mustang dyno is known for its very low numbers. At 15.9 psi using very old 200 treadwear dunlop direzza ziii tires (the same ones it auctioned with in Japan) with no burnout and driving through some water overspray it ran 12.2657 seconds at 117.34 mph with a 1.9499 second 60 with a very novice driver (me). Currently I think I have an exhaust restriction because I can't get the boost any higher on the street even though the waste gate is at 100% duty. In a few weeks I will have an electric cutout installed and attempt another tune and see how that effects the dyno numbers and 1/4 mile time. I have read a rule on some time attack sites to add 15% to convert a mustang to a dynojet, perhaps I will take it to a dynojet at some point to see. The ecu isn't just about power though, it's about the rolling antilag (not that I need it), launch control, canbus to bti gauge, datalogging, fuel pump control, canbus to keypad, flex fuel control, etc etc.
92 mph trap in the 1/8 is about exactly what I would expect from a FD making 350-370 rwhp on a dynojet. I imagine you are correct and will pick up 8-10% numbers on a typical dyno jet dyno. I bet at 20psi on the track you would trap 95-96 in the 1/8th. Anything above 90 is a quick street car. Anything at or near 100 in the 1/8th is a whole lot of fun on the street. Not bad for a 30+ year old platform with stock ports. Well done.
How does it drive? How’s the spool compared to the stock twins? Are you happy with the turbo?
It drives great, spools really quickly and I am overall very happy with the turbo. I definitely got exactly what I asked for, but can't help but wonder if the 8374 would have just been all around better. I chose the 8370 because I wanted a strong amount of bottom end power and response so that my V8 swapped FC didn't outshine it. It will be interesting to see what kind of total boost, power and trap speed it will make with the exhaust cut out, hopefully can update in about 3 weeks.
Do you get a harmonic ringing noise between coasting and cruising? I used to get that on my 7670 and my buddy does with his, but I don't have that issue with the 8374.
Do you get a harmonic ringing noise between coasting and cruising? I used to get that on my 7670 and my buddy does with his, but I don't have that issue with the 8374.
So I got the electric cutout installed but did not fix my problem.
Looks like it's actually the waste gate spring so I will need to get the correct one installed.
During the dyno pull, the clutch was slipping pretty significantly. I can only assume that the previous owner in Japan had a stock clutch in the car since it was on stock twins. I was doing a bit of research here on the forums, especially about lighter flywheels and what I have gathered so far is most people in most circumstances are happier with the lighter flywheel, assuming the car was not a dedicated drag racing car. I don't ever plan on putting drag radials on the car, upgrading to a t56 or anything else like that. So I can't imagine a 60ft time will ever really be a priority. Therefore, with that kind of limit, what do you guys suggest on a flywheel / clutch setup that could hold potentially 25 psi and a future street port (lets say around 500hp max) without being an ON/OFF switch? Or at least the best compromise? I see a lot of positive posts about the streetlite and prolite from ACT with the streetlite being preferred.
I know that having the transmission dropped I will also replace anything that is serviceable like the transmission seals and throw-out bearing, rear main seal etc etc but if anyone has any suggestions let me know.
The biggest hold back is the 0.92 housing. That is likely a bigger restriction than the exhaust. Just as the BW turbine sizing graph indicates, the AR flow potential is directly tied to the frame size. You can see on their graph that the 0.92 size on the 74 frame turbine is four flow division lines higher than the 0.92 frame turbine you’re using. My projection is that it never achieve 500 whp no matter what. I still say an EFR 8370 can’t achieve 500 whp on a 13B even with the largest 1.05 AR housing. If it does the EMAP will be through the roof.
Pretty simple to see; just determine where a 13B - 8374 @ 500 whp is on the turbine graph and compare it to the 70 frame turbine flow lines. It simply can’t get there without a larger AR housing, if it could ever be large enough at all.
.
The biggest hold back is the 0.92 housing. That is likely a bigger restriction than the exhaust. Just as the BW turbine sizing graph indicates, the AR flow potential is directly tied to the frame size. You can see on their graph that the 0.92 size on the 74 frame turbine is four flow division lines higher than the 0.92 frame turbine you’re using. My projection is that it never achieve 500 whp no matter what. I still say an EFR 8370 can’t achieve 500 whp on a 13B even with the largest 1.05 AR housing. If it does the EMAP will be through the roof.
Pretty simple to see; just determine where a 13B - 8374 @ 500 whp is on the turbine graph and compare it to the 70 frame turbine flow lines. It simply can’t get there without a larger AR housing, if it could ever be large enough at all.
.
When I first read your response I was fairly confused because I have never claimed that it will be achieving 500 whp. I did say "So I can't imagine a 60ft time will ever really be a priority. Therefore, with that kind of limit, what do you guys suggest on a flywheel / clutch setup that could hold potentially 25 psi and a future street port (lets say around 500hp max) without being an ON/OFF switch?" When I said (lets say around 500hp max) I am talking about the clutch rating, which I did make a typo where I said HP instead of TQ. When I say max, I am saying I don't think I would need anything with a higher rating as I only expect to make 400whp. So I would be happy with a 450tq or a 500tq rated clutch but not a 700tq rated clutch, leaves room for improvement if I ever decide to swap to the 8374 as well.
In regards to the restriction vs the housing, I should have clarified something. It made 20psi on the dyno, in 4th gear, but while drag racing "At 15.9 psi using very old 200 treadwear dunlop direzza ziii tires (the same ones it auctioned with in Japan) with no burnout and driving through some water overspray it ran 12.2657 seconds at 117.34 mph with a 1.9499 second 60 with a very novice driver (me)." It won't get to the 20 psi on the street/track, according to my data logging results. Now I said for the clutch, potentially hold 25 psi, just incase there are some improvements to be made. The tuner who has done various FDs with 7670s, 8370s and 8374s had an expectation of 25 psi, perhaps he was thinking of a different housing? Currently the wastegate says its at 100%ish duty cycle. I would still like to see if I can get any improvements fixing that.
I do appreciate the informative response, what do you think max psi it should deliver be then?
When I first read your response I was fairly confused because I have never claimed that it will be achieving 500 whp. I did say "So I can't imagine a 60ft time will ever really be a priority. Therefore, with that kind of limit, what do you guys suggest on a flywheel / clutch setup that could hold potentially 25 psi and a future street port (lets say around 500hp max) without being an ON/OFF switch?" When I said (lets say around 500hp max) I am talking about the clutch rating, which I did make a typo where I said HP instead of TQ. When I say max, I am saying I don't think I would need anything with a higher rating as I only expect to make 400whp. So I would be happy with a 450tq or a 500tq rated clutch but not a 700tq rated clutch, leaves room for improvement if I ever decide to swap to the 8374 as well.
In regards to the restriction vs the housing, I should have clarified something. It made 20psi on the dyno, in 4th gear, but while drag racing "At 15.9 psi using very old 200 treadwear dunlop direzza ziii tires (the same ones it auctioned with in Japan) with no burnout and driving through some water overspray it ran 12.2657 seconds at 117.34 mph with a 1.9499 second 60 with a very novice driver (me)." It won't get to the 20 psi on the street/track, according to my data logging results. Now I said for the clutch, potentially hold 25 psi, just incase there are some improvements to be made. The tuner who has done various FDs with 7670s, 8370s and 8374s had an expectation of 25 psi, perhaps he was thinking of a different housing? Currently the wastegate says its at 100%ish duty cycle. I would still like to see if I can get any improvements fixing that.
I do appreciate the informative response, what do you think max psi it should deliver be then?
This is typical with TeamRX8s responses - fixate on a point and figure out a way to tear it down rather than be constructive and read in to the spirit of what someone is saying - so don't sweat it. Your target and ask is reasonable though its going to be skewed because clutches don't slip based on horsepower, they slip based on torque, and you'll be making more torque lower than most 500 horsepower single setups. Everything I've heard about ACTs 'new' twin disk setup is that its the bees knees though I haven't dealt with one personally - I believe ACT is trying to do more high brow engineering over it's old standby of 'clamp the **** out of it, pedal feel be damned' so thats nice.
Ok, I possibly read too far into the OP’s comment about 500 whp/mid-20+ boost level on the clutch inquiry. If so, it couldn’t possibly be an honest mistake given all the past comments and claims in this very forum section regarding the EFR 8370, right?
Regardless, it doesn’t change the fact that the 0.92 housing poses a major restriction on the 70 turbine paired to a 13B engine when exceeding 15 psig boost. At the 20 psi he already ran it at, it’s likely a lot higher than anyone here realizes. And again is going to be more of an issue than the exhaust system. Any personal opinion about me is irrelevant. As was once wisely cracked in one form or another, I have no desire to sing koom-bah-yah along with any tribe that would even consider having me as a member of their sanctimonious choir 😅.
Neither does it do away with the intended and implied technical merits of the post. If the intention is to help, then suggesting that he install and monitor an emap device would have served that purpose better. Nobody asked me, but if they did then my response would be that nobody in the tribe is picking up on where this engine is operating at on the BW turbine graph emap scale at 20 psig boost.
.
So in lighter news, just for a cool comparison... I took my 383 swapped FC3S to the same dyno and the comparison is pretty wild. Earlier in the thread I mentioned I didn't want my V8 car to outshine the FD while street driving where this car spends most of its time.
The graph is a little skewed to the left on the RPM for some reason, as the test ended at 6500rpm.
Last edited by JaredCarpenter; Nov 3, 2025 at 03:24 PM.
Reason: Photo not displaying
I am not sure why I am having a hard time getting this photo to display, but anyway the 383 is a gen 1 small block, 10:1 compression, AFR 195 heads, AFR single plane port matched intake, hydraulic roller cam 239/247 .567-.581 and 108 LSA, Holley Super Sniper EFI kit with a Hyperspark ignition and it only made 4 less horsepower and 22 more tq. The graphs look basically identical with the V8 car having more torque between just 2 and 3k rpm. Not bad for the 8370 on stock ports to make 6.2L V8 torque and power.
