RXSpeed16

iTrader: (41)

I have all the parts, I'm just trying to decide what to use on a stock ported s4 TII engine: Hybrid T04B S-trim vs S5 stock.

1. Would a T04b S-trim hybrid turbo hold boost at high rpm better than the S5 stock ht-18 turbo?

2. Does the v-trim wheel actually improve response over the s-trim or stock turbo? Based on the compressor maps, the v-trim seems ideal for a stock port motor, but I'm not sure how exactly that translates to the real world.

Some background:
So I finally decided to open up the blown T04b hybrid I've had on the shelf and was disappointed to find an S-trim wheel inside. From what I've gathered, the T04b s-trim and stock compressor have similar outputs with a slight nod going to the s-trim. I'd be thrilled with 300hp @ the flywheel, but that seems like a pretty lofty goal for this turbo. That's also the ceiling for the rest of my fuel system and longevity of the car. The compressor inlet has also been modified to accept the 2.5" stock turbo inlet duct, so it is no longer a great candidate for a big power build. It is, however, great for an upgraded stock look I'm going for. I have driven with the s-trim turbo, but its 25 year old bearings failed in under 10k miles. So I don't know if there is a difference between new and whatever condition I got it in. Anyways, I'm seeing if I can get a modest power bump, increase the power band into the upper rev's and lower IAT's without losing the responsiveness of the turbo. Thanks.

j9fd3s

iTrader: (3)

here is the stock compressor map, so you can compare. no idea what unit Gc is.

the S wheel seems like it does 300flywheel@10psi...

RXSpeed16

iTrader: (41)

IF Gc = 10lb/min, 200hp is about where the stock turbo maxes out at 1.6 bar (~9 psi)...makes sense to me.

Seeing how hard people have pushed the stock turbo, I wouldn't be surprised if the S-trim can put out 300 up at about 20 psi or so. It just makes me nervous to run that high with the stock pressure sensor and Rtek timing maps.

It does seem to be a nice happy turbo for 250hp @ 10psi though. I am concerned about running the turbo hard outside its efficiency ranges since I'll be using the TMIC.

Unless there's some glaring problem I'm overlooking, looks like I'm going to go with the hybrid s-trim.

RotaryRocket88

iTrader: (7)

An S-trim has both a larger inducer and exducer than stock, and since a stock turbo is capable of around 300 BHP (~250 WHP w/ 17% drivetrain loss), it should be plenty capable of that goal.

Since that stock turbo map has unknown units, we can also estimate from a similarly-sized wheel. A T3 50 trim is just slightly smaller on both the inducer and exducer.

Stock compressor: 63 x 43.68 mm, 48 trim
Garrett T3 50 trim: 60.12 x 42.52mm

8 Blade T04B
Garrett PN, exducer x inducer, trim, flow
409179-0021, 70 x 48.36 mm, 48 trim, S trim (37 lbs/min)
409179-0025, 70 x 55.37 mm, 63 trim, V trim (48 lbs/min)

http://www.squirrelpf.com/turbocalc/map.php
https://www.rx7club.com/showthread.p...ht=stock+turbo

Garrett T3 50 trim



S-trim map



V-trim map



If you plot a point at 1.7 pressure ratio (10 psi) and 30 lbs. per min. airflow, the T3 is somewhere around the 50% efficiency island, the S-trim is in the 60% region and the V-trim is at 70%.

I can tell you that my V-trim feels no less responsive than stock, but it builds much more torque and pulls much harder to redline. Datalogs show at least 25% more peak airflow according to the AFM, and that's at only 10-11 psi by redline. It's more efficient than my stock compressor was, but at the same time I'm cramming more air through the TMIC. IATs are similar to stock during short pulls, but it heatsoaks more easily. Water injection will be my cure.

RXSpeed16

iTrader: (41)

^Awesome info yet again. Thanks.

bumpstart

284 RWHP ( DD dyno ) at around 1 bar ( leaky gauge ) is the best i have seen from a s4 , s trim highflow with modified internal gate and modified backing plate
( one of my motor and turbo builds )

faster spool than V trim but still not as good as stock

2-N-D-pink

iTrader: (27)

Im curious to know if anyone experiences surge with with the V trim. The reason why I ask is because Im using the stock compressor map vs the V trim.

Looking at the stock compressor map it shows 1500 rpms is a little less than .5 on the X axis. It then lines up around 1.2 on the Y axis. On the stock compressor map, it starts to reach the 75% efficiency range when the X axis meets the number 1 and the Y axis around the 1.4.

When you compare the numbers to the V trim wheel you are in the surge area at those two points (X axis = 1 and Y axis = 1.4) Who knows what RPM youre in at this point but it is not the most amount of air your engine produces (redline) and its definitely in the surge area.





Lets not forget to about atmospheric air pressure.
Pressure Ratio is defined as absolute outlet air pressure divided by absolute inlet air pressure.

In my case here in Florida the atmospheric pressure = 14.7. So If I where to boost 10 psi on the v trim and I want to find out what pressure ratio is going to land me in, I would use this equation.

absolute outlet pressure + boost pressure divided by absolute air inlet

So 14.7 + 10 psi divided by 14.7 = 1.68 (round to the nearest tenth) = 1.7.

But if you are at a higher altitude let say 5000ft above sea level then your ambient air pressure would be 12.4. In that case then you would use this equation.

12.4 + 10 psi divided by 12.4 = 1.8

This points out that you would need MORE air for a given PSI than at sea level, so they are working harder for a same pressure level than a turbo would be at sea level.

RotaryRocket88

iTrader: (7)

1.4 pressure ratio = 6 psi boost, and you'd have to be making that off-idle (somewhere around 1-1.5k RPM according that stock map). That's never going to happen.

Well, yeah, but if you want to compare compressors you need to use the same pressure measurements for each. 1 atmosphere is defined as 14.7 psi. Changes due to altitude will affect any compressor.

reo

iTrader: (4)

Good info. have a s5 t-ll with street port and haltech going together. also have an s trim compressor and housing. altitude is mostly from 3k to 9k. Am i going to get into trouble with the s trim using the stock top mount ic? Car weighs 1400#

j9fd3s

iTrader: (3)

well yes, you will get into trouble, 300hp in a 1400lbs car!

actually if you were to give the stock IC more/better airflow it'll help

reo

iTrader: (4)

am 70, so cautious, no different than 2800lbs and 600hp and perhaps much smoother. as for IC; i have a larger one but in order the priorities are water, oil and then charge. the radiator uses most of the frontal area and by fabricating a new nose cone i can use the stock fc oil cooler behind about 8" and slightly higher with a scoop and duct over the radiator and if needed will also use a beehive, it is going to be rough getting air to the stock ic and it seems to be the opinion on this club that using a different cooler could be not as good, will experiment with that and have 2 stock ICs if it comes to that. but just hate to add weight.