Reducing Turbo Lag

[dbo]

Ok.. I tried a search but couldn't find too much to answer my question.

My main question is... what is the best way to reduce turbo lag on my RB20? I'll give you a quick rundown of the situation.

I have a 4 door R32 GTS-t, with:

GT25R Turbo (Dual ball bearing, steel turbine rated to 450hp)

Re-mapped ECU

Custom FMIC with alloy piping

Possibly HKS dump pipe, with high flow cat

3 1/4" exhaust whole way through

Apexi AVC-R

Thats all I can think of at the moment. I love the turbo, but it seems to start spooling so late and is really laggy untill it does spool. It starts to make boost at around 3000 rpm and hits full boost (1 bar) at about 5200rpm.

In the near future i'll be upgrading the injectors, fuel pump and possibly a fuel pressure regulator, as my injectors are pretty close to max duty cycle (thats what it feels like anyway)

Will these mods help with my low down power significantly? Or should I be looking at a set of cams to help with low rpm torque? Is my AVC-R set incorrectly i.e should my turbo be spooling quicker than that?

I've heard of people clipping turbo fins and things like that, but i'm not interested in playing round with the turbo. I'm hoping that with the FPR installed I should be able to run abit more fuel lower in the rpm range and get abit more torque.

I'm hoping to get about 220rwkw once the new parts are in. I'm at about 190rwkw at the moment.

Correct me if i'm talking crap, as i'm not as experienced as most members on this forum.

Cheers.

[Roy]

Sadly its a simple equation...2L engine equals so much exhaust gas. A 450hp turbo requires X amount of energy to spin it. For a 2L motor to provide sufficient exhaust gas/energy you need to rev the thing.

Only real way around it is go smaller turbo, bigger engine, or appreciate that you only have 2L and you have moved the powerband up the rev range.

Outside of that you can get a nicer tune, try cams, try cam gears, try a smaller exhaust housing, there are a bunch of little things, but you will never be able to make use of a 450hp turbo whilst avoiding what you are calling lag....there is always NO2

[rev210]

Cams help.

If you don't have upgraded injectors get some and a fuel pump too.

[rev210]

On the other hand why not forget about the rpm that the turbo kicks in at and go for decreasing the physical 'time' in seconds that you wait for the turbo to kick in or the engine to acheive rpm.

To do this you can aim at droppping the rotational mass of the engine/drivetrain.

Lightweight flywheel / lightweight pulleys / Electric thermofan with thermo switch / carbon fibre tail shaft / light weight forged alloy wheels etc...

[dbo]

On the other hand why not forget about the rpm that the turbo kicks in at and go for decreasing the physical 'time' in seconds that you wait for the turbo to kick in or the engine to acheive rpm.

To do this you can aim at droppping the rotational mass of the engine/drivetrain.

Lightweight flywheel / lightweight pulleys / Electric thermofan with thermo switch / carbon fibre tail shaft / light weight forged alloy wheels etc...

<{POST_SNAPBACK}>

Ah ha now this man is a thinker! some good idea's I should look into...\

Is anyone else running this turbo?

[Roy]

not arguing, but wouldnt a change in diff ratio be much cheaper and easier then all of that stuff?

[dbo]

not arguing,  but wouldnt a change in  diff ratio be much cheaper and easier then all of that stuff?

<{POST_SNAPBACK}>

Comments like that make me think I should have thought about this alot more hahaha

I may aswell ask this in the same thread, but it is abit of a n00b question.

What diff comes standard in an R32 4 door GTS-t? As I've heard so many conflicting stories..

I'm goingto be after a new diff soon... but I don't want a big clunky 2 way or anything.. but something that looks well and will allow abit of drift action

[Sydneykid]

Ok.. I tried a search but couldn't find too much to answer my question.

My main question is... what is the best way to reduce turbo lag on my RB20? I'll give you a quick rundown of the situation.

I have a 4 door R32 GTS-t, with:

GT25R Turbo (Dual ball bearing, steel turbine rated to 450hp)

Re-mapped ECU

Custom FMIC with alloy piping

Possibly HKS dump pipe, with high flow cat

3 1/4" exhaust whole way through

Apexi AVC-R

Thats all I can think of at the moment. I love the turbo, but it seems to start spooling so late and is really laggy untill it does spool. It starts to make boost at around 3000 rpm and hits full boost (1 bar) at about 5200rpm.

In the near future i'll be upgrading the injectors, fuel pump and possibly a fuel pressure regulator, as my injectors are pretty close to max duty cycle (thats what it feels like anyway)

Will these mods help with my low down power significantly? Or should I be looking at a set of cams to help with low rpm torque? Is my AVC-R set incorrectly i.e should my turbo be spooling quicker than that?

I've heard of people clipping turbo fins and things like that, but i'm not interested in playing round with the turbo. I'm hoping that with the FPR installed I should be able to run abit more fuel lower in the rpm range and get abit more torque.

I'm hoping to get about 220rwkw once the new parts are in. I'm at about 190rwkw at the moment.

Correct me if i'm talking crap, as i'm not as experienced as most members on this forum.

Cheers.

<{POST_SNAPBACK}>

Hi DBO, a GT25R is not a bg turbo, you should be seeing boost build around 2,750 rpm and full boost by 3,500 rpm in 3rd gear. There are few things that concern me in your list of upgrades;

A. "Re-mapped ECU", how good is the tune? Got any dyno graphs? We need RWKW, torque, boost and A/F ratios. If you don't have them, go to the next club dyno day, pay $$50 or so and get them. Post them up, there are plenty of guys on here who can read a dyno graph and give suggestions.

B. "Custom FMIC with alloy piping", refer to #3 below.

C. "Possibly HKS dump pipe", that doesn't fill me with confidence, is it split or combined dump? What about the engine pipe?

What to do;

1. More fuel is not going to do anything for boost build, in fact if is already running rich it will just make it worse.

2. If it will take it, my first suggestion would be more ignition advance

3. Check the restrictions in the inlet system, compare the boost at the compressor outlet with the boost at the plenum.

4. Try dropping the exhaust just before the cat on the dyno and see what difference it makes (one 10 second power run will reveal a lot).

5. Disconnect the vacuum feed to the turbo and compare the boost build. That will tell you whether the wastegate and boost controller are doing the job of keeping the wastegate closed until the target boost is reached. Be carefull, you have no boost control when doing this test. It is a boost build test to the target boost, stop when the target boost is reached.

6. Once you have the turbo building boost as it should, then start thinking about other items. Find the problem first and fix that, if you keep throwing random parts at it you will just muddy up the water.

Hope that helps

Cheers

Edited February 16, 2006 by Sydneykid

[Roy]

Will these mods help with my low down power significantly?

<{POST_SNAPBACK}>

Significantly, my undestanding of his expectation is it wont change it significantly. You no doubt can improve the response/power of the thing once its on boost, (if it starts spooling at 3,000rpm, it shoudlnt be taking until 5,200rpm to hit 1bar)

It will only ever make Pulsar type power between idle and 2,500rpm...and they are never that special between 2,500, 3,500rpm. From what i have seen turbos liek 2530 (320hp) really only ever boogie from 4,000rpm (even if they have hit 1 bar at 3,600rpm). I know mine is makign 17-18psi around 4,200 somewhere, but nothing happens until 4,500rpm and up

Is my AVC-R set incorrectly i.e should my turbo be spooling quicker than that?

<{POST_SNAPBACK}>

Take it to a reputable workshop who has experience turbo cars...they will work it out pretty quickly...forums are great for DIY information, but you cant go past taking it to the experts if you have the coin.

[dbo]

Jesus you fella's no your skylines well...

I will be taking her to get tuned soon.. but I though i'd ask around first and see what the best solution in reducing lag etc would be..

And yeah.. she makes 1 bar at around 5200.. not sure if my gear based learning in the AVC-R is holding her back or not? Might take her to WASP performance or somewhere on the coast for a decent tune, as I don't know how well the ECU was remapped etc..

[Roy]

At the end of the day, i suppose im just tryign to temper your desire to get more bottom end. You did say bottom end, not mid range etc.

Some things suggested are things you should check as a matter of course of getting a new setup working well. Other will cost thousands amd may only result in a small improvements, when a smaller turbo liek a 2510/2530 willdo everything you need without having to worry about expensife pulleys, flywheels, thermo fans etc etc.

A better question is how much power do you ultimately hope to make...

[Chris32]

As everyone has suggested, makes sure the basics are sorted out first

I would strongly advise that you get it on the dyno and see what the AFR's are like.

Going from my experience with a 'remapped' ecu, it made me think my car had a much bigger turbo than it really did

A simple upgrade of injectors and PowerFC, and a bit of tuning, transformed my car from being very laggy to having very little lag at all

A decent tune makes all the differance!

Check out the overlay on this graph, notice the mid-range gains of optimised AFR's and ignition timing

What is not shown is the old remapped tune would run at about 15/1 AFR's in the mid-range, and little timing due to detonation

Now it runs more timing, with AFR's around 11.5/1

Thats where my 'laggy' feeling was, and it was all in the tune

[dbo]

WEll.. I love the feel of the current GT25R.. and it is good for 22psi which MAY happen one day..

I'm hoping in the end to have close to 260rwkw running about 1 bar, but also something that has a nice response.

[Sydneykid]

At the end of the day, i suppose im just tryign to temper your desire to get more bottom end. You did say bottom end, not mid range etc. 

Common Roy, it's an RB20DET;

Bottom end = 2,500 to 4,250 rpm

Mid range = 4,250 to 6,250 rpm

Top end = 6,250 to 8,250 rpm

Under 2,750 rpm is not bottom end, it's IDLING RPM. :lol:

Cheers

PS; if it was an RB31DET then;

Bottom end = 1,500 to 3,000 rpm

Mid range = 3,000 to 5,500 rpm

Top end = 5,500 to 7,500 rpm

Edited February 16, 2006 by Sydneykid

[Roy]

Common Roy, it's an RB20DET;

Bottom end = 2,500 to 4,250 rpm

Mid range = 4,250 to 6,250 rpm

Top end = 6,250 to 8,250 rpm

Under 2,750 rpm is not bottom end, it's IDLING RPM. :lol:

Cheers

PS; if it was an RB31DET then;

Bottom end = 1,500 to 3,000 rpm

Mid range = 3,000 to 5,500 rpm

Top end = 5,500 to 7,500 rpm

<{POST_SNAPBACK}>

LOL....Ok

But i never even get near 5,500rpm in day to day driving. so i suppose when i hear bottom end i think the rpm you are pulling in traffic

When you are up the thing, who really cars what your bottom end is like, its only in day to day hustle and bustle when i need to shift back to 2nd at 45km/h to get past a car i curse the RB20

[Drift_Mulisha]

Yo, just a thought here but would you consider going down an exhaust housing size? i assume you have the .86 housing on your GT25R if it is the 450hp version? I have the 400hp version with the 0.64 housing on an RB20 & find the spool pretty reasonable for the size of the turbo. i im getting boost build from 3000rpm with full boost (currently only 12psi due to injectors maxing out & not being tuned) at 3800rpm. which was enough to make 195kw atw. I have no doubt that this setup once tuned should make 230-240kw atw using 18psi. if your aim is only 220kw atw then i would definately change to the smaller exh. housing as that amount of lag is not worth it for that power output.

Peace.

[dbo]

From what i've been reading I have a suspicion that my car needs a decent tune.. Because she won't make even 0.5 of a bar at say 4200 rpm...

Anyone recommend a good place to get a dyno tune on the gold coast?

[rb20inside]

Yo, just a thought here but would you consider going down an exhaust housing size? i assume you have the .86 housing on your GT25R if it is the 450hp version? I have the 400hp version with the 0.64 housing on an RB20 & find the spool pretty reasonable for the size of the turbo. i im getting boost build from 3000rpm with full boost (currently only 12psi due to injectors maxing out & not being tuned) at 3800rpm. which was enough to make 195kw atw. I have no doubt that this setup once tuned should make 230-240kw atw using 18psi. if your aim is only 220kw atw then i would definately change to the smaller exh. housing as that amount of lag is not worth it for that power output.

Peace.

<{POST_SNAPBACK}>

yer would definitly go the 0.64 exhaust housing on the 20. the 0.86 seems to be as you described, 'laggy'. i think the 0.64 is a much better matched turbo to the rb20. try 'quincy777' as i believe he has a gt28rs (0.64) on his rb20.

check out: http://www.skylinesaustralia.com/forums/in...topic=92622&hl=

From what i've been reading I have a suspicion that my car needs a decent tune.. Because she won't make even 0.5 of a bar at say 4200 rpm...

Anyone recommend a good place to get a dyno tune on the gold coast?

<{POST_SNAPBACK}>

although i havent been there myself. my mate took his car to PITS on the gold coast and was very pleased with his result.

Edited February 17, 2006 by rb20inside

[Dee 33]

From what i've been reading I have a suspicion that my car needs a decent tune.. Because she won't make even 0.5 of a bar at say 4200 rpm...

Anyone recommend a good place to get a dyno tune on the gold coast?

<{POST_SNAPBACK}>

P.I.T.S

[1400r]

check your cooler piping Ive been chasing a lag issue on my car for 12 mths now and it "looks" like it was due to a leak from the cooler piping

ps my cars been on 3 different dyno's and was never picked up