Wheres My Midrange?

[gt-ahhh!]

hi all

i recently swapped out my motor and bolted up a new turbo etc to go with, ecu, dyno tune etc etc. problem is, the car seems to lack midrange power. it makes plenty above 5000rpm, which is nice, but the turbo should really be making its power from 3500rpm.

R33 RB25DET standard

gcg hi-flow turbo

480cc injectors + pump

fmic

greddy copy plenum

3in split dump + gutted cat

3.5in cat back

ebc

splitfire coilpacks

ems stinger ecu with map sensor

my run is the highest blue line without dots. i plotted two lines (with dots) above that to show comparisons from other RB25s who are also running gcg hi-flows at 16-18psi.

as you can see, theyre making 25-40kw more than me in the midrange, but almost identical peak power. this is very irritating since the whole reason i chose that turbo was so the car would be more responsive!

im at a bit of a loss as to how i could be losing this power, so ill outline some possible weaknesses of my setup.

-ems stinger ecu. running batch injection and waste spark. i realise this is not perfect, but all the information ive read tells me this shouldnt be a major problem.

-small throttle. the intake piping to the throttle is 3in, but the factory throttle is only 2.5in. would this be a big restriction? doesnt seem to affect peak power...

-soft wastegate. with the ebc off, boost only gets up to about 10psi. but with the ebc on the dyno the car makes 18psi at 3600rpm so i doubt this is a problem.

-pod filter sucking engine bay air. im going to get some cold air into that soon.

-boost leaks. theres a few small ones i am aware of so im in the process of replacing silicone joints etc. despite making 18psi at 3600rpm, if small leaks force the turbo to work harder in the midrange, will keeping the wastegate closed longer restrict exhaust flow/power?

should i ask them to have another go at tuning it?

[gt-ahhh!]

any help or advice greatly appreciated!

[krzysiu]

If you want more midrange for your setup i would get an adjustable cam gear. Does help a lot. Also an illegal way of gaining midrange power is removing the cat.

Without a cat my car makes 30rwkw more in the midrange!

*edit: just saw you have a gutted cat, replace it with a straight pipe with the cat shell welded on top.

[adis]

off topic question, but can i ask, why did you upgrade the injectors to 480cc injectors? As far as i understand, standard ones are good for 230-40kw arent they? Or is that future mod, for more kw? just curious

[PM-R33]

Ok first of all you are right, that midrange for a GCG highflow is shit house, so you are correct that you need to find what is wrong.

Boost is coming on and holding fairly well, so it aint a boost/wastegate issue.

The thorttle aint the issue at all so don't worry about that.

And the pod sucking in hot ait also aint the problem so don't worry about that.

Have you ever had the timing belt off and replaced? If so are you sure the cams are dialled in correctly?

What piping do you have from the pod filter to the turbo? It aint sucking shut is it?

Edited January 19, 2010 by PM-R33

[TiTAN]

how much ignition timing have they used in the mid range? does the VCT still work?

[GTScotT]

EMS makes me think there is a VCT issue, also tune could be a BIG thing.

my money is on the combination of both, so realistically its all tune related.. maybe put the stock ecu back in and have the EMS piggy back (to retain VCT etc)

[R31Nismoid]

random points, no particular order.

1. Tune, given the graph isn't all that smooth i wouldn't be surprised if it had a fair bit to do with it

2. Cam timing/belt could be off. Is VCT working?

3. Intake piping sucking shut

4. Cooler? What type?

5. You said boost leaks. If you are seeing 18psi @ the plenum AFTER boost leaks, you'll be making who knows what @ the turbo (eg 24psi). This could well be heating the air far to much.

6. Stock throttle body can flow 350rwkw+, so that's not a problem.

7. Drop the exhaust from before the CAT, just to see what happens (before/after dyno run)

8. You do need a better actuator. Personally i would be getting a 1bar/14psi actuator on there at some point.

[Dose Pipe Sutututu]

1. post up your timing map, looks like there's crap all timing at low rpm

2. post up your A/F graph

I recommend adding more gain to your EBC @ 12PSI, the boost at 16PSI looks pretty good

R31Nismoid, don't think the intake pipe is sucking shut, you wouldn't get full boost all the way on the rev range.

[R31Nismoid]

Doesnt have to suck totally shut to restrict the airflow or create issues due to pipe shape changes etc - just something to check either way that wasn't mentioned, 5 sec on a dyno to rule something out

[PM-R33]

I was thinking the VCT could be the issue aswell but it seems to be ok up until about 3500rpm, i would expect with the VCT not working at all that there would be a substantial power drop below 3500 aswell. Do EMS ecu's control VCT?

[Dose Pipe Sutututu]

saying if it doesn't the power shouldn't look that bad.. I believe the tuner hasn't been bothered to tune the low/mid parts of the map..

Post up:

1. your timing map

2. your torque curve vs power/boost

[gt-ahhh!]

  adis said:

off topic question, but can i ask, why did you upgrade the injectors to 480cc injectors? As far as i understand, standard ones are good for 230-40kw arent they? Or is that future mod, for more kw? just curious

they were on the plenum/fuel rail when i bought it second hand. also, yeah just a good upgrade to have up my sleeve.

[gt-ahhh!]

  PM-R33 said:

Ok first of all you are right, that midrange for a GCG highflow is shit house, so you are correct that you need to find what is wrong.

Boost is coming on and holding fairly well, so it aint a boost/wastegate issue.

The thorttle aint the issue at all so don't worry about that.

And the pod sucking in hot ait also aint the problem so don't worry about that.

Have you ever had the timing belt off and replaced? If so are you sure the cams are dialled in correctly?

What piping do you have from the pod filter to the turbo? It aint sucking shut is it?

thanks for your input.

yes the timing belt and head gasket were replaced when i put this motor in. so thats a very good point, i will have to ask my tuner about that.

the suction pipe is the factory one, clamped onto a z32 afm which is not wired up since im using a map sensor.

[Harey]

  adis said:

off topic question, but can i ask, why did you upgrade the injectors to 480cc injectors? As far as i understand, standard ones are good for 230-40kw arent they? Or is that future mod, for more kw? just curious

Also interested to see the answer to this...

[gt-ahhh!]

sorry this was a dud reply.

but i may as well use it to reanswer the injector question.

they were on the plenum/fuel rail/motor when i picked it up second hand.

and yeah, nice to have up my sleeve if i ever go for more power.

Edited January 20, 2010 by gt-ahhh!

[gt-ahhh!]

  R31Nismoid said:

random points, no particular order.

1. Tune, given the graph isn't all that smooth i wouldn't be surprised if it had a fair bit to do with it

2. Cam timing/belt could be off. Is VCT working?

3. Intake piping sucking shut

4. Cooler? What type?

5. You said boost leaks. If you are seeing 18psi @ the plenum AFTER boost leaks, you'll be making who knows what @ the turbo (eg 24psi). This could well be heating the air far to much.

6. Stock throttle body can flow 350rwkw+, so that's not a problem.

7. Drop the exhaust from before the CAT, just to see what happens (before/after dyno run)

8. You do need a better actuator. Personally i would be getting a 1bar/14psi actuator on there at some point.

thanks. i will definitely hit up the tuner after the last few posts. i have no idea whats going on with the timing and vct etc etc. that was the only dyno printout i got.

intake pipe is factory item.

cooler is hybrid 600x300 with 3in outlets.

i thought the cat might have been blocked, so i went for a drive minus the exhaust lol. lots of noise, but no extra power.

in regards to air temp, they should be able to check this on the dyno yes? the ecu has air temp correction i believe.

[R31Nismoid]

  Harey said:

Also interested to see the answer to this...

GCG hi-flow will make more power than factory injectors... simple really.

plenty of GCG hi-flows making 250-260rwkw

[Beer Baron]

looks like poor tune to me as it's making the right boost at the right time. could be a cam timing problem though too. also what headgasket went back in? standard size or thicker?

[gt-ahhh!]

  Beer Baron said:

looks like poor tune to me as it's making the right boost at the right time. could be a cam timing problem though too. also what headgasket went back in? standard size or thicker?

probably standard size. why do you ask?