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Less power (slower) after turbo upgrade!!! WHY?

nedb

By nedb,
in Engines & Forced Induction

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nedb Proficient

nedb

Posted
Posted

Hi, I hope the following post will make sense, as I’m quite disturbed to write.

Recently I did a turbo swap on my RB20. I put a RB25 turbo which was in good condition. From what other ppl said, the RB25 turbo makes 10 – 20 rwkw more than the stock one.

I just had a few runs with my mate, laser with mazda-familia engine, and he was beating me more than before the turbo swap.

He ran a 14.1 at the creek and he is a consistent driver, so all the times are within 1 sec. Before the turbo swap he would be beating me 1 – 2 car lengths but this time he got me 3 – 4 car lengths. His setup hasn’t changed at all.

My car is R32 – auto with only a pod and RB25 turbo. It’s running 9 psi.

I didn’t put the car on the dyno before the conversion so the only means of comparing the power output is against his car, and so far it doesn’t look good. I was hoping to at least even out with him, with the new turbo setup.

Also, I got a 0 – 100 km/h option on my turbo timer and even that is showing I’m about 1 sec slower than before.

I'm almost tempted to put the old turbo back on and go for a power run on the dyno.

Does anyone have any ideas why would my car go slower than before and how to fix it?

Please HELP!!!

predator Grand Master

predator

Posted
Posted

you are only running fairly low boost.. the point at which the rb25 turbo hits its efficiency range on the rb20 may be different to the stock turbo, so that could be the situation.

Have you had it tuned since the upgrade? its not going to give an instant 10-20rwkw just by sticking it on, without the appropriate tune.

nedb Proficient

nedb

Posted
  • Author
Posted

Thanx for the replies guys

predator:

i haven't had it tuned yet, i'm waiting till my new exhaust goes in.

i was under impression that i should get more power from the turbo upgrade even on stock boost but maybe i was wrong. I hope it's just that and not some other problem.

Jay95R33:

I’m running the rb20 actuator, so 9 psi. I don’t have the boost controller yet but getting one.

meggala:

I did try to run him rolling start as well but he was still pulling away. Quite different from the stock turbo, coz then he would have an advantage at the start, up to 100 km/h where our speeds would be about the same and I’d start catchin up, but now he gets ahead at the start and stays there, maybe even keeps pulling away. Very annoying.

does anyone else have any ideas?

ppl who have done this conversion, what were your results on stock boost with rb25 turbo compared to the stock boost with rb20 turbo and on the increased boost with both?

Cubes Grand Master

Cubes

Posted
Posted

I've had a VG30 on my RB20t and even though it made more power in the top end general street use was much slower than the boosted RB20t turbo.

First gear with the vg30det sucked arse. It felt like it was soo hard to make it make some decent boost.

I've been in a blokes car who was running a RB25 turbo. He pumped in around 13-14psi.

My 164rwkw RB20DET felt like it had a stronger mid range and accelerated quicker, BUT it wouldn't keep pulling past 7000rpm like the the rb25det turbo would.

I wasn't happy with the mid range from the rb25t turbo on the rb20det so I decided to scrap the whole idea of spending $$ on a turbo for the rb20det. Hence the build up of my rb30det.

The rb20det with the stocker turbo running 16psi would get me to 100km/h in a shade over 5secs with a real clean launch. A bad launch would typically be in the mid to high 5sec range.

The VG30 turbo only lasted 3 days before I pulled it off and put back the rb20t turbo.

Its the power to peak power that accelerates the car not the peak power. :D

You will find with the setup you have now the rb20t turbo gave you more average power over the usable RPM than what the rb25t turbo does.

Keep pumping boost in to it until it fuel cuts then back it off a little. :D

BUT make sure you have an aftermarket fuel pump, you wouldn't want the stocker leaning out.

Then throw it on a dyno for a power run (~$40) and make sure the AFR's are not leaning out. If so just back boost off a little :)

Also... you may have some restriction in the exhaust somewhere as my rb20t only ever made 8-9psi with the stock exhaust and stock fist sized cat convertor.

As soon as I had the exhaust fitted boost raised to 10.9psi.

Doctor Mentor

Doctor

Posted
Posted

Do yourself a favour and get a 3 inch exhaust from the dump or including dump. You cant expect the turbo to be working at its best if it cant breath properly. 9psi did nothing for me with the rb25 turbo. It really starts to howl once over 11psi.

Before you start winding the boost up though, get your AF ratios checked on the dyno.

Doc

Ronin Experienced

Ronin

Posted
Posted

I have a rb25 turbo on my r32 and make 180-190rwkw depending on the day. I also have hks super dragger zorst, dump, chip remap, pod, fmic, blitz sbc iD. I run 14psi.

It is a bit laggier than the stocker obviously and the power delivery is different, its more progressive than all at once like the stocker. Pulls much harder up top than the stocker did.

nedb Proficient

nedb

Posted
  • Author
Posted

Thanx guys on the replies.

I'm planning to get the exhaust done this weekend - turbo back and then on the dyno, to be safe before i boost it up.

Can anyone recommend any exhaust shops in sydney, preferably west but not essential.

Also, dyno places?

Thanx.

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