Advice on GT28RS supporting mods

[mjeazy4784]

hey, I'll be installing my engine this week sometime but ive got a few nagging questions... the turbo on the engine was blown when I got it, so I read around and decided to get a GT28RS to replace it (assumed rebuilding the stock one is a waste of money). what size injectors would work best? definately a walbro 255 going in as soon as I get it running. will a SAFCII or SAFC NEO and wideband be sufficient for tuning? I'm looking for 200-220 whp for the car, so not really big league or anything. also i'm assuming that i dont need any of this to start the car up for the first time, since it wont be boosting or anything. my plan is to get it running correctly w/o boosting and then add the upgrades to make the turbo operational just incase there are any problems along the way.

and a quick wastegate question, turbo is wastegate sprung at 14 psi apparently , doesn't that mean that i CANT run less than 14 psi? if thats true would it be a bad idea to swap the wastegate pot and bracket off the stock T25 and put it on the GT28RS? (i'd guess that the wastegate would then be sprung at 7ish psi?)

[sideways danny]

i ran mine at 9psi on standard ECU no problemI then added a good chip and turned it upto 13.5 psi and got flywheel 294bhp (injectors maxed at this)

[mjeazy4784]

damn nice numbers there, how were you able to run 9psi? did you change the wastegate?

[nocwage]

13.5psi on a GT28RS netted you 294hp???That seems a little high for that turbo, what other mods did you have?

[matty]

get an oil cooler

its wont net you any ponies but it will be a damn good supporting mod for that turbo you got there.

[sideways danny]

13.5psi on a GT28RS netted you 294hp???That seems a little high for that turbo, what other mods did you have?

2 years worth of part collecting, research and re-engineering.

wiseco pistons, lightened balanced bottem end, flywheel lightned 4.5kg. KA24 throttle body, low compression UK spec ported head (quench pads removed, chambers balanced), port matched inlet manifold, CA18DE inlet cam. Frenchweapon tubular manifold, 3 inch thick FMIC (painted black) custom breather system, 1.3mm ACL head gasket, RPS max street organic clutch, 2.5 inch scorpion exhaust system. Greddy ProfecB, re-mapped Eprom.

dyno figure recorded on a DynoDynamics rolling road generally regarded as the most accurate in the UK

294.1bhp/ 242ft lbs

[rico05]

I hate you. That tq # is NICE. I hope to get near that soon myself...

[sideways danny]

I hate you. That tq # is NICE. I hope to get near that soon myself...

torque is disapointing actually, it went flat because the fueling started to lean out, I think 315bhp and 270 ft lbs is easy with bigger injectors and 15psi. I want to push past 350 bhp at about 22psi really but that will take some careful mapping

[float_6969]

Why did you remove the quench pads, was it to decrease the compression even further?

[sideways danny]

Why did you remove the quench pads, was it to decrease the compression even further?

to dtop the compression to keep EGT's down and to reduce the places for detonation to occur. as standard the clearance piston to head is too big and actually encourages detonation. I've seen a lot of detonation scars on quench pads. Doing this means I can run more advance safer and not mess with expensive thick metal head gaskets. I used a 1.3mm ACL gasket that i sourced from Australia for much cheapness I'm running 8.17:1 CR

[float_6969]

Is the clearance not in the .040" range? Why not simply deck the block or use a thinner headgasket to bring it down to where it needs to be? Quench pads are a proven idea and used on all modern day, high output motors. They have a definate purpose, and are useful.

I'm not saying your wrong for removing them, I just don't want members removing the quench pads on their heads because they think it's a good idea and don't understand what they are/what they do.

Also, did you gain horsepower by running more advance? Advance timing doesn't = more HP in every scenario. I'm sure you know what you're doing, I'd just like a litte more info. I've never heard of anybody removing them. I've heard of them being enlarged in V8 heads, but never reduced/eliminated.

[sideways danny]

standard clearance is 0.048" (standard gasket being 1.2mm) which is too big a gap to be effective. you need to run in the .025-.035" range for it to work, but I'm not clever enough to work out things like rod stretch when running tight tollerences so took a different option. it's not the right way for everyone and I've built a lot of engines in the conventional way and they've worked fine. I wanted to be different with mine which is why it took me 2 years to be unconventinal in the right way.

most people here drop compression to be able to run high boost. I didn't want to go as low as some do, (7.8:1 sometimes) this was the best way for me. in this situation quench pads are purely an emissions control device for a normal car, they are also the first place detonation will occur. I was told it was crazy, that it would never work and that I was ruining my head but it takes big balls to break the mould. I've never been one to follow the crowd

my injectors are maxed out completely, there's no more power available without more fuel so I think that the extra advance has yeilded exactly what i wanted, response low down and the ability to run more boost (when I get bigger injectors fitted I believe that I now have the highest BHP recorder on standard injectors (370cc) without raised fuel pressure, in the UK it's not my daily drive setup, I have it at 10psi for normal use, running lots of boost without adequate fuel would be silly

[dash]

interesting approach. Good combo for the 28rs

[float_6969]

wow, .025 is the kind of clearance that they run on race motor that get rebuilt regularly. That is actually close enough that the piston and head actually just barely "kiss" eachother at higher RPMS. I dissagree that the clearance has to be that tight for them to work, as most stock applications are right at .040. A street/strip motor would be pretty safe at .035. And the whole point of quench pads is to help reduce knock. They induce swirl in the combustion chamber and help to eliminate hot spots on the piston surface.

Regardless, more power to you and your motor, and congratulations on your HP acheivement!