Backpressure vs Turbo Lag

[Py7h0n]

With a MA70 that will be the case.

With a GA70 the base torque will drop.

2.5" should still be enough for the power you are making - Going any bigger will drop your low end torque.

How about provide dyno sheets to prove that theory....

I've seen dyno sheets that prove otherwise. Think it was on a 7MGTE MA70 supra. a guy dyno'd with a 2 1/2 inch, then with a 3 inch, same boost levels, no other mods. Picked up a couple of HP down low and 10-20HP in some areas. The normally aspirated exhaust laws go out the window as soon as you put a turbo into the equation

[strx7]

Why not swap out the 1G for something nicer like a 1JZ out of an MA70?

a 1JZ would come out a of a JZA70........

[Lith]

With a MA70 that will be the case.

With a GA70 the base torque will drop.

I bet a marmite sandwich that you can't back that up

[fivebob]

I have to drop it into 2nd and get the rev's to around 4K before boost will come up and I'll be able to accelerate.....

WTF are you doing driving below 4000rpm and expecting a big turbo to spool instantly... get real, even a reasonably sized turbo isn't going to perform much below 3500rpm

[cat007]

Why not swap out the 1G for something nicer like a 1JZ out of an MA70?

1JZ out of a MA70? Yeah - righto.....because that makes sense.....

Why don't I then after I've done that, go for something nicer, like a VR38DETT, and then after I've done that, go for something nicer than that, like a blown 540ci Hemi crate motor......

I'm sorry - but when people say "why don't you go 1JZ - you'll get more power" - just makes me mad, and laugh at the stupid question. It's a real tyre kicker question......

[cat007]

With a MA70 that will be the case.

With a GA70 the base torque will drop.

I bet a marmite sandwich that you can't back that up

Or maybe, a Mo-mite sandwich haha

actually - that sounds kinda gross - "who wants a Moustache ride?" "oh I do I do"

haha

Sorry - O/T

[cat007]

WTF are you doing driving below 4000rpm and expecting a big turbo to spool instantly... get real, even a reasonably sized turbo isn't going to perform much below 3500rpm

I don't get ANY boost until about 4K - as in, sitting at 3,500rpm in 3rd up the hill, foot to the floor, the car just sits there, same speed, 0-1psi, maybe 1-2 IF I'm lucky.....

I'm not expecting 15psi by 4,000rpm - I understand that's a bit of a tall order hehe. But some sort of mid-range would be nice. All my power is made from 5,000rpm - there's seriously, nothing, below 4K

[Lith]

actually - that sounds kinda gross - "who wants a Moustache ride?" "oh I do I do"

And its around this time of month I really wish I found an adventurous Swedish lass hitchhiking on the way home. Dreams are free I hear there is a sequel coming...

That lag does sound pretty nasty, though reasonably consistant with what I have heard of happening with similar sized turbos on RB20DETs. I know RB20 people hate their motors being associated with 1GGTEs and vice versa but results for both motors seem very very consistant with each other. If you really can't tolerate it there are 3 most obvious suggestions:

1) Get a smaller turbo
2) Get a bigger motor
3) Run more boost and make power suited to the turbo size and justify the lag

[cat007]

Not at all! I think the RB20 is a great motor! If I were a nissan bloke, that's the engine I'd focus on.

albeit they aren't as strong as a 1G - they're still a 2L straight 6 that can make a fair bit of power

Yeah - I think I just need to get over it and run more boost and never go below 4,000rpm

[strx7]

Can you post more details of your exact set up? ie: engine specs, compression ratio, std cams? diff ratio? factory ecu or aftermarket etc etc etc?

3rd gear 3500rpm up a hill and only just getting +ve manifold pressure sounds like something is a bit amiss somewhere

[cat007]

Can you post more details of your exact set up? ie: engine specs, compression ratio, std cams? diff ratio? factory ecu or aftermarket etc etc etc?

3rd gear 3500rpm up a hill and only just getting +ve manifold pressure sounds like something is a bit amiss somewhere

Engine is standard internally, just new rings and bearings.
Compression ratio is 8.0:1 (using 1G-GZE pistons which I'm told are 8.0:1 as opposed to the 1G-GTE's pistons of 8.5:1)
Using 1G-GE cams - which give slightly more lift and longer duration
Intake manifold is stock, but apparently it has pretty good flow.
T-VIS isn't hooked up, I have yet to find an actuator and solenoid
Diff ratio is 4.5:1, although I had a 3.9:1 and had the same issues.
Using a Stinger 4424 ECU tuned by Kent at SpeedSource.

I'll do a bit of testing/logging tonight if I can. Otherwise might be tomorrow

Cheers
Hunt

[matt dunn]

Compression ratio is 8.0:1 (using 1G-GZE pistons which I'm told are 8.0:1 as opposed to the 1G-GTE's pistons of 8.5:1)

The lower the compression, the worse the lag.
I got full boost 1000rpm earlier by going from 8.0:1 to 8.9:1

Using 1G-GE cams - which give slightly more lift and longer duration

Cams that also wont be helping the low end response,

Intake manifold is stock, but apparently it has pretty good flow.

Maybe good flow, but NA manifold and FI manifold designs are quite different,

T-VIS isn't hooked up, I have yet to find an actuator and solenoid

Have you ever drive an Early 4AGE without the TVIS hooked up?
There is absolutly no power down low without it,
That's the first thing you would want to try.

Using a Stinger 4424 ECU tuned by Kent at SpeedSource.

Have you asked them about the tune,
as it may have been tuned for power and reliability, not throttle response,
and the area you are having problems is the main area of detonation so it may have no advance in there to be safe.

[cat007]

The lower the compression, the worse the lag.
I got full boost 1000rpm earlier by going from 8.0:1 to 8.9:1

Yeah - I would've liked to have stuck with the 8.5:1 GTE pistons - but I broke a ring landing (this was before I went standalone)

Cams that also wont be helping the low end response,

They shouldn't affect bottom end that much though.....

Maybe good flow, but NA manifold and FI manifold designs are quite different,

It's a standard GTE manifold....I thought the N/A and GTE manifold's were the same.....?

Have you ever drive an Early 4AGE without the TVIS hooked up?
There is absolutly no power down low without it,
That's the first thing you would want to try.

Ok - I'll track down some T-VIS gear and hook it back up.

Have you asked them about the tune,
as it may have been tuned for power and reliability, not throttle response,
and the area you are having problems is the main area of detonation so it may have no advance in there to be safe.

I think it is a safe tune - running quite rich, not sure about the timing - the map does look pretty tame.

[touge rolla]

Why not swap out the 1G for something nicer like a 1JZ out of an MA70?

you mean JZA70

[escortman]

yeh without tvis if its like a 4age turbo will have crap down low

[2jayzgte]

If your going to stick with the 2 litre I would base all my gains in the lower and middle of the rpm range basically better response.So basically base your turbo and mods to improve this area.On the track Torque is the key not out and HP.

Slightly off topic but this is how I have gone about modifying my MKIV alot have people go with Single Turbo set-ups but I have chosen to stay with the factory twins and concentrated all of my attention in this area as this involves getting out of corners quicker where your single turbo set-ups don't really start humming until you get 1/2 way down the straight and by this time your gone.

[cat007]

yeh without tvis if its like a 4age turbo will have crap down low

well the 1G is just like a 6 cylinder 4age

I'll try and source all the tvis parts today and put it on.

I guess I'll just have to have a play with when to turn it off, then set one of the aux outputs to turn it off at a certain rpm, like 4,200 etc...

[strx7]

I believe, the way to get the best performance out of any turbo'd vehicle is to be able to tune the vacuum mapping when its N/A

be extracting the most from an engine before +ve manifold pressure is introduced, you'll get the best off boost responce, and faster spool.

running 8:1 compression ratio, at no manifold pressure, at from 2000rpm an above you should be able to have around 30 degrees of advance, possibly even as much as 35 degrees.

[mjrstar]

i suggest the exhaust manifold pipe diameter is killing it for lag, it looks like you are running 1 1/2 inch pipe manifold, i run 1 1/4 pipe on mine with a plain bearing turbo and have usable boost 5-6psi at around 3700rpm. (i also run non turbo compression ratio)
if it is 1 1/4 disregard my comments...

I also ran a 2 1/2 exhaust for a while, it didn't do much at all to lag but it decreased the engine braking ability with a less restrictive exhaust...

the dyno was in 4th gear before i put the taller diff in it. and i run a smaller diameter tyre so you can count on about 26kph/1000rpm

[cat007]

i suggest the exhaust manifold pipe diameter is killing it for lag, it looks like you are running 1 1/2 inch pipe manifold, i run 1 1/4 pipe on mine with a plain bearing turbo and have usable boost 5-6psi at around 3700rpm. (i also run non turbo compression ratio)
if it is 1 1/4 disregard my comments...

I also ran a 2 1/2 exhaust for a while, it didn't do much at all to lag but it decreased the engine braking ability with a less restrictive exhaust...

the dyno was in 4th gear before i put the taller diff in it. and i run a smaller diameter tyre so you can count on about 26kph/1000rpm

Is that 1 1/4 ID or OD?

I would measure mine - but that'd only show the outer diameter and I'm not taking my manifold off - still sorting the GTT 'dina clutch lol