Rb20 Dyno Comparisons

[nisskid]

ok so over the time ive had my car ive had it dynoed 3 times, the first time was at turbo tune, hadnt had the car long, only had a 3" catback exhaust, besides that bone stock, had a few missing issues, but by the time it was fixed i got 150rwkw. the next time was at boostworx, nothing really major to report there, and finally i went to get a remap which was done at turbo tune by the speed lab, at this time i had now got a very high flowing turbo back exhaust, FMIC, pod, Bosch 040 and most importantly i had upgraded to a RB25 turbo from the original rb20 turbo. i received a before and after print out, the before was actually running a base map so not a full comparison but gave me a good idea. from the mid 150rwkw's with just the base map in with the rb25 turbo, it went to 182rwkw which i was pretty happy with, but still didnt resolve the big issue i had with lag of the rb25 turbo, now a bit more lag was expected even though it would receive a 3" dump and decat along with the new turbo aswell as the tune, but the amount was still very annoying. so i thought id chuck all my dyno sheets together and compare them on one chart. the result was fairly rough but gave me an idea.

Green: First dyno, stock RB20 Turbo

Red: Third dyno, rb25 turbo, base map

Blue: Third dyno, rb25 turbo, full remap and tune

Left Power, Right torque

Left Power, Right pressure

now ever since the rb25 turbo has been installed there has been a rattle that comes from the wastegate that comes on when decelerating in gear and in general low revs. i sussed it out and found that when i pull up on it, it almost feels like it clicks into place and stops rattling, only problem is after the wastegate is opened and close again it goes back to the original position. now this leads me to think there is a leak and its not sealing properly at low revs, and this would explain a massive difference in lag.

whats everyones thoughts on this?

original dynos:

[CEF11E]

when the car is cool, get a good strong set of pliers and grip the actuator rod and try to pull it towards the dump pipe. Is it firm to really hard to move? does it wobble at all or does it feel loose?

if it all feels OK

to bring the boost on sooner try using a turbotech boost controller as the ball and spring mechanism will not net the actuator open at all until the desired boost is reached. it is an easy way to eliminate wastegate creep.

your power figure is really good. but you are right there seems to be a fair bit of lag. you have given a lot of useful info unlike a lot of the "what is wrong with my car" threads.

Also check to see if all the clamps leading to the actuator are tight and there are no splits or pinholes in the hose.

boost control looks good from the graph what are you using to control it?

Have you still got your RB20 actuator? it will suply more preload and may also help spool the turbo earlier.

worst case scenerio, you could pull the dump pipe and check the flap is seating properly.

Hope this helps

[Kane_R32]

May I ask what you torque is in NM? Both stock and at present?

Cheers.

[nisskid]

  Kane_R32 said:

May I ask what you torque is in NM? Both stock and at present?

Cheers.

yes in NM, they are obviously missing a 0 on the end.

[nisskid]

  CEF11E said:

when the car is cool, get a good strong set of pliers and grip the actuator rod and try to pull it towards the dump pipe. Is it firm to really hard to move? does it wobble at all or does it feel loose?

if it all feels OK

to bring the boost on sooner try using a turbotech boost controller as the ball and spring mechanism will not net the actuator open at all until the desired boost is reached. it is an easy way to eliminate wastegate creep.

your power figure is really good. but you are right there seems to be a fair bit of lag. you have given a lot of useful info unlike a lot of the "what is wrong with my car" threads.

Also check to see if all the clamps leading to the actuator are tight and there are no splits or pinholes in the hose.

boost control looks good from the graph what are you using to control it?

Have you still got your RB20 actuator? it will suply more preload and may also help spool the turbo earlier.

worst case scenerio, you could pull the dump pipe and check the flap is seating properly.

Hope this helps

yeh it doesnt feel loose any other way but up and down. im using the cheap turbotech controller seen in that massive thread, it does do a good job, the first dyno doesnt use it but the other 2 do use the controller.

last time i checked there werent any obvious problems apart for the C clip on the end of the rod which was gone and i replaced that.

yes im still using the rb20 actuator, im starting to think i should try and source out a rb25 one just to try and see if i have the same issue.

im thinking of taking off the dump and checking it, but the amount of issues i had with putting the dump on (snapped off a bolt in the housing and ended up making one of the threads useless, so i sealed the dump with a silicone as well as the gasket) im not so keen to take it off in a hurry. when i had the turbo off it seemed like it was in pretty decent condition so id be kinda surprised if it was a fault with the turbo.

[Green_s13]

i would try another actuator, i dont seem to have any more lag than what i did with the rb20 turbo on my car, however i have a friend who's is laggier both have rb20 actuators.

i doubt your dump would cause this, you would hear the exhaust leak and wouldn't make that amount of power.

[nisskid]

  Green_s13 said:

i would try another actuator, i dont seem to have any more lag than what i did with the rb20 turbo on my car, however i have a friend who's is laggier both have rb20 actuators.

i doubt your dump would cause this, you would hear the exhaust leak and wouldn't make that amount of power.

alright cheers. yeh im not saying its my dump causing it, its just i cbf taking it off to check as its going to be a bitch to get back on and seal.

[Green_s13]

fair enough, i guess the other thing is did you replace your turbo to manifold gasket when you swapped the turbo over?? if this was reused, it could have a slight leak, i doubt it but it is another option

[nisskid]

yeh i reused all my gaskets, they seemed fine when taken off. as said the rattle noise is definitely coming from the wastegate as when i play around with the actuator rod it stops and starts.

[nisskid]

any other ideas?

[Ceffy_SA]

Sounds like you have the same problem as i did with my turbo, the waste gate as not sealing on the turbine housing letting exhaust gas bypass the exhaust turbing through the leaking waste gate.

I could hear the waste gate "flap" rattling on the turbing housing when cruising around, all i did to fix it (a bit dodge) was bend the waste gate accuator arm outwards so that it was applying more force to the waste gate making it seal.

Boost response went from 15psi at around 3800rpm to around 3200rpm, just make sure you dont bread anything if your going to bend the waste gate accuator arm and you dont go too far so it fouls on anything.

Edited August 30, 2007 by Ceffy_SA

[nisskid]

yeh it sounds like the same issue, i was thinking of modifying something but thought i might try some other actuators aswell.

cheers

[Ceffy_SA]

That would do it i think, your current one may not have enough travel in it to fully close the waste gate flap allowing exhaust gasses to escape past it creating more lag.

[sky30]

As CEFFY SA said, its probly the wastegate flap not sealing tight. i also had this problem, just grab the actuator rod with pliers and use a big screwdriver to put a bend in the middle, this will pull the gate flap shut tighter and fix the problem. Takes like 1 minute to do and makes the car feel so much better to come on boost.

[nisskid]

mm might just do that, the question is whether i risk it and try it tonight before the track day tomoz or not haha.

[Cubes]

I elongated the bolt up hole (top hole only required) on my rb20 actuator. Big screwdriver to push the actuator towards the front of the engine bay (away from the turbine housing) to apply as much preload as you wish then tighten up the actuator bolts.

Takes little adjusting but with no boost controller I had mine running ~15-16psi for quite a few years using that method.

Also didn't drop boost.

It worked so well that I sold my Blitz SBC-iD III EBC which I now regret doing with my current setup.

[nisskid]

^^alright cheers, that sounds like a less dodge way haha, ill go suss both of them out now.

[The Dan]

Don't bend, that is the most rediculous thing you casn do. do as Cubes suggests and elongate the holes. Then just move the pod away from the turbo. You should need to pull the rod arm the width of it's hole to get it over the wastegate arm. It should be firm and hard to pull out.

[nisskid]

well i took it off, filed out the hole, i went to put it back on and it doesnt reach the wastegate arm, so i need to pull the rod out of the actuator to fit it onto the arm?

[Cubes]

Loosen the bolts slightly; connect the actuator arm to the wastegate.

Shove a big arsed screw driver inbetween the comp cover and actuator. Lever the actuator away from the turbo (actuator to the front of the car) and nip up the bolts.

Then drive carefully and see what boost your running, pull over slightly adjust and see again.

I ended up marking the actuator rod where it enters the actuator for easier rough adjustment.

From memory mine required ~5mm preload for ~1bar.