rustydusty1717

could anyone tell me roughly what the max power is on a greddy 18g turbo? i recently pulled my motor and looking at building the top end a bit and installing an LSD in my tranny. but i would just like to know what the max power that the 18g will put out so i can either get a new turbo or keep my 18g. also does anyone know the easiest way to make a new downpipe for the 18g? the cast one that greddy includes in the kit is very restrictive.

TheShodan

iTrader: (14)

The turbo is good to about 640cfm at 2.0 pressure ratio (a little over 20psi), so up to about 380, but it must be severely pushed. It's good to about 44.5lbs/min, a little less than a 20g. The issue is the turbine flanging and actuator. the flapper door on the Greddy 18g prevents you from maximizing its potential, unless you convert it to an external wastegate.

rustydusty1717

380 whp? so if i kept it internal wastegate what would you say the max whp i'd get out of it without getting into trouble. like i said i'm looking at building my top end a bit. valve springs, retainers etc etc. and the reason i'm building my top end more is for more boost and if my 18 G won't be able to put my top end build to use then i'll need to upgrade.

quicksilver1689

with a freeflowing downpipe and all other things in check, 300-330whp is attainable. or just removed the wastegate and go to external gate, do you have the greddy cast manifold? that can be a bottleneck.

rustydusty1717

ya i'm looking at making my own downpipe instead of using the greddy cast one. i'd rather not change the wastegate if i didn't have to. i'd like to see 300 WHP or more. yeah i have the greddy cast manifold. does anyone make a manifold for the greddy turbo's that i could purchase? also is 2.5inch exhaust too small for 300-325 WHP? i just got it all done couple months ago and i'd rather not change it. also will i have to upgrade my BOV for more power also or no? it's the greddy type rs.

TheShodan

iTrader: (14)

Yes. In order to get higher than over 300whp, you will have the change the wastegate, and more importantly, the Flapper door, since it is only 32mm (very small).

As for the 380whp possible, that is over 2.0 pressure ratios. Unless you have the managment for it, it will be more like about 300-325 MAXIMUM, with external gate.

3" exhaust is best for 300whp +. 2.5 is rather a restriction. The cast manifold can easily do that power. upgrading BOV will not solve anything for power.

rustydusty1717

how hard is it to do external wastegate? i would need a new manifold in order to do that wouldn't i? so the internal wastegate wouldn't be able to handle 300 whp?

90 JDM EF8

iTrader: (1)

i did the external wg, its not hard you just have to buy the right parts and weld the internal wg shut,you need a t25 to t3 adapter if you dont get a custom manifold made with a t25 flange on it, and also a gt28 3" v-band flange for downpipe from atpturbo, i went from 295hp with internal wg and greddy manifold to 350hp with ramhorn manifold and external wg, heres a pic for you...

quicksilver1689

damn good numbers^, your manifold choice and external gate choice really helped to extract some good power out of that turbo, do u have a dyno chart? id love to see that powerband. good work

blaze the chemi

Check out this thread. It's about the greddy kit and what people have done to their setups.
https://honda-tech.com/zerothread/1836946

Contact UrbanSi He had this kit and had a custom DP made. I think he got rid of A/C, which you probably don't need up there in Alberta.

I had the kit for a long time too and enjoyed it for DD. I surprised many at only 248 whp (12 psi).

Any reason you are building your head and not the bottom end? Most of the B series honda heads flow great already. Build the bottom end especially because of our weak ringlands.

90 JDM EF8

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quicksilver1689 &raquo;</TD></TR><TR><TD CLASS="quote">damn good numbers^, your manifold choice and external gate choice really helped to extract some good power out of that turbo, do u have a dyno chart? id love to see that powerband. good work</TD></TR></TABLE>
new dyno on external wg


old dyno on internal wg

rustydusty1717

for the record i have no AC. i ripped it out a long time ago. anyone know of anyone who makes a tublar manifold for these 18g turbo's? i could get one made but i'd rather just buy one that's been done perfect. also if i left the waste gate internal could i get 300 whp out of my turbo? or do i have to go external. i'd rather not have to weld the internal wastegate to go external but if i have to i will.

TheShodan

iTrader: (14)

You will need to go external to get over the 300whp mark, bottom line. Check with those that make tubular external wastegate manifolds using a T2 flange system.

rustydusty1717

so the greddy 18g's use a T2 flange?

thatblkguy

yes it does

rustydusty1717

just talked to a few mechanics at my local speedshop and they said the internal wastegate should be fine. external is best but the internal should be fine for just as much as the turbo can do. anyone agree with this? or are they just yanking my chain?

thatblkguy

TheShodan is right in what he has told you.

rustydusty1717

so if i get a new manifold made and i keep it internal wastegate what would be the max numbers i'd see. as long as i see 300 WHP i'm happy. now as far as headwork goes what should i look at doing to make sure it does go kaboom. i only wanna do what i need to do to make it reliable.

fastcody1

but the point is if you go with an external wastegate you can make more power and have much better control over the boost
the internal valve is so small and has such a tight radius to make once it leaves the turbo it causes turbulence
in my op it's worth the extra money to get the turbo to come on sooner without worring about spiking and creeping

90 JDM EF8

iTrader: (1)

if you get a different manifold made then why wouldnt you just make it external wg for a couple hundred extra bucks more and if you stay internal wg you will have boost spike sooooo bad like i did before i went external, look at my two dyno sheets i posted and you can see how much better the power band is external wg

rustydusty1717

i'm probabally gonna make my own manifold. also how much boost are you running on the internal and external wastegate? and how much was the boost spiking on the internal wastegate? and finally how did you make the downpipe? i wanna make my own also out of 2.5 inch pipe but not sure how to get it onto the turbo itself.

90 JDM EF8

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rustydusty1717 &raquo;</TD></TR><TR><TD CLASS="quote">i'm probabally gonna make my own manifold. also how much boost are you running on the internal and external wastegate? and how much was the boost spiking on the internal wastegate? and finally how did you make the downpipe? i wanna make my own also out of 2.5 inch pipe but not sure how to get it onto the turbo itself.</TD></TR></TABLE>

on dyno i was at 15lbs external wg and 14 internal wg, i dont exactly remember how much spike there was cuase it was like almost 2 years ago but it wasnt nice...in order to get rid of the whole greddy neck dp itself you need to order the atpturbo.com garret gt28 internal wg 3" v-band downpipe flange, but you will have to trace out your gasket from the greddy dp on the new flange and really take a lot of the flange off the inside to be able to have the internal flapper open all the way...or you can keep the restrictive 2.0" greddy neck and just make a dp from there with a 3 bolt flange

TheShodan

iTrader: (14)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 90 JDM EF8 &raquo;</TD></TR><TR><TD CLASS="quote">

on dyno i was at 15lbs external wg and 14 internal wg, i dont exactly remember how much spike there was cuase it was like almost 2 years ago but it wasnt nice...in order to get rid of the whole greddy neck dp itself you need to order the atpturbo.com garret gt28 internal wg 3" v-band downpipe flange, but you will have to trace out your gasket from the greddy dp on the new flange and really take a lot of the flange off the inside to be able to have the internal flapper open all the way...or you can keep the restrictive 2.0" greddy neck and just make a dp from there with a 3 bolt flange</TD></TR></TABLE>

There is a premade flange from Garrett that fits this when going to the 3" v-band. Many others have also attached the wastegate AT the downpipe and kept the Greddy manifold, which is more than capable of the power he's looking for.

The internal wastegate from greddy is NOT just fine. The flapper door is only about 32mm opening that only opens about 70 degrees instead of a full 90 degrees.

rustydusty1717

okay guys. thanks for all the help on the wastegate issue. i've made a decision now. now as far as the head goes what all should be done to make the motor able to handle all this boost? valve's, springs, retaainers, seats etc? also do i need to machine the head and get it bored out 1 mm and get bigger valves?

quicksilver1689

no