Are you going for a street car? I would reccomend the 7 cm housing. After reading all the reviews of the 8cm housing with the fp 68 HTA and how crappy it was and my experience with my bastard 20g the 7cm would be the way to go imo
Just my 2¢

Yes it will be street driven with occasional drag time. And yeah I just got done reading a thread about how full boost doesn't come on til 4k at 25psi..that sounds terrible. I dnt get how the 8cm^2 housing can be that laggy tho.

I'll be running the turbo with 264/272 cams as well so idk if that will help in recommendations. I just dnt want the turbo to run out of steam in the upper rpm range like Ive been reading with the the 16g around 6k and up.

But I know however I may not get the best of both spool and top end.

I have a big 16g and its great but falls flat on its face above 6k. but I get full boost (tuned @ 22 psi) before 3k rpms makes for a really fun in town beater. quick spool w lots of tire shredding action

Seems like I'll be right in the sweet spot then with the 18g compressor wheel. If you're getting 22psi before 3k rpm then I'm not too worried where the 18g spools up as long as its decently below 3.5k rpm. What was your hp at 22psi?

Tigerinstincts said:

Seems like I'll be right in the sweet spot then with the 18g compressor wheel. If you're getting 22psi before 3k rpm then I'm not too worried where the 18g spools up as long as its decently below 3.5k rpm. What was your hp at 22psi?

Click to expand...

320 on a gst

Here's some food for thought.

The 18G compressor design is older than the Evo III 16G compressor, falling directly in-between the identically-designed Big 16G and 20G wheels. An Evo III 16G wheel is about the most-efficient cast compressor design out there considering weight / hub size / aero tech / airflow for it's size.

The MHI Evo III is capable of flowing the near the same, or even greater than the 18G in some situations thanks to it's design...assuming you have the supporting mods to let it do so. The Evo III 16G doesn't need a turbine housing larger than 7cm2 or any kind of fancy turbine clipping to let it perform to it's peak, either.

Despite the Evo III's more-efficient compressor, the inducer is still smaller....meaning the compressor trim number is lower than the 18G, so it's physically compressing/heating the airflow more than the 18G per revolution of the wheel. A cooler air charge can indeed translate into more power depending what type of fuel you're using and how good of a tune you have...but as a drop-in on a stockish car the Evo III 16G is definitely going to feel faster due to the quicker spool and subsequent higher torque.

More data to reinforce the performance differences between an off-the-shelf Evo III 16G and 18G with a higher-flowing turbine...this 18G would've had a 7cm2 housing, but a larger TD06SL2 turbine which would effect power output in a similar manner to a larger turbine housing a/r: http://www.dsmtuners.com/threads/fp-18g-6sl2-dyno-results.491697/


SO- if you want a turbo with the best all-around performance and usable airflow, go for the Evo III in the 7cm2 housing. If you're going for high boost, max power, or using a poor quality fuel that can let you run into a knock wall earlier in the boost range from turbine backpressure, then go with the 18G in the 8cm2 housing and free up the turbine side a bit. A FWD car would also favor the slower spool / less-torquey hit of the 8cm2 housing as well.

Thanks for your input Justin, I was sorta hoping you'd find this thread and lay down all of the variables. I do plan on running high boost eventually for either of these turbos as I have all the supporting mods to max out both of their potentials but it looks like its still a tradeoff between better response vs better top end and both are going to be similar.

Here's some pics. Evo lll 16g on left/Greddy 18g on right.
18g is definitely heavier than the 16g...and I ddnt realize how much bigger the 18gs comp housing was until now.

Quick question, I'm about to assemble both of these turbos finally and I was wondering can I use the 18g wheel and the turbine it came with in the Evo iii 16gs chra housing? The reason I'm asking is the 18gs original chra housing didnt come with water ports. I feel it's fine but just want to double check.

yes you can. I disagree with the stuff justin says about the 18g wheel. calling it a dud and having no place in the mhi line-up. I have used the greddy 18g in its original form that was sold for 2g cars 5h/8cm. I have also used it with the greddy cold side 6h/6cm. the later was one of the funnest turbos I have used on a 2.0. justin seems to be bench racing just from looking at and measuring the wheel. I go by using it. I would run the wheel over the evo 16g everyday of the week and twice on sunday. the lag difference is minor. the way it pulls to redline 7500 is HUGE.

I would check the batteries on your scale. I have measured the evo 8/9 wheel at 57 grams, and the evo 3 at 63 grams if i remember right. the 18g at 69 and the 20g at 71 (my guess is your scale is reading low and your 18g is not MHI but kamak replacement that looks identical but weighs 5-7 grams more) I would bet 1000 dollars there is not 15 grams between the two.

there also a guy on here that years ago made 450/450 dynojet on e85. he used one the 18gs the FP offered for a short time. with 6sl2 turbine. the setup was nothing all out. pretty average run of the mill. 9/1 2.0 with 272 cams intercooler 3in exhaust.

I'm going by my butt dyno and i am thrilled with the peformance of the MHI EvoIII .and all i've done is bolt it in .comes on strong across the rpm range starting at 3000 all the way to 6500 rpm. i run the street with it .

94awdcoupe said:

justin seems to be bench racing just from looking at and measuring the wheel.

Click to expand...

Bench racing from measuring wheels and linking a thread to a user of the FP TD06SL2 18G you referred to in your last paragraph where the user made less power on pump gas with the 18G and seemed a little disappointed overall at it's performance in comparison to the Evo III 16G? When composing a direct comparison of two turbos it doesn't get much more "direct" than running them on the same car on the same dyno.

Either turbo serves it's purpose. The Subaru platform seems to love 18G's but they also haven't had an affordable (well, "formerly" affordable) direct-fit turbocharger using an Evo III 16G compressor available as a bolt-on upgrade for the past two decades. That being said, I don't know anyone who would set out to upgrade their Evo III 16G to an 18G...doesn't meant that it's not a worthy wheel, but with the 20G not far away I'm certain most interested parties would just skip the 18G altogether.