Turbo or Atmo

Its all about horses for courses. Some circuits (tight twisty ones especially) suit cars with good throttle response, the more long straights you get the more the turbo comes into its own. Atmos tend to handle better as they have more linear power delivery. I think standard atmo and turbo GTA's would be pretty evenly matched around your average circuit. Atmo would be more fun in standard form though.

[Alpineandy]

What's the weight difference?

Check out "The Cars" section from the RH menu......

Dunno if these are any good ,my work comp has decided it doesn't like Flash again
http://www.youtube.com/watch?v=ysTje2jOjEg
http://www.youtube.com/watch?v=oJAWR9BOwPM

Sounds like the sound is late compared to the visual. He changes gear then about 2 seconds later you hear it!

Good videos!

Wish he'd put his steering wheel back on straight though!


Nice bit of hillclimbing here too:

http://www.youtube.com/watch?v=N1Xh6vful-8

No nanny state in France----------no frecking speedbumps

Blipping the throttle aids gear change when going down,
Matching revs concept. But as to aid turbo lag not so sure you can rev the engine all you like the turbo will only spin when under load.(i.e in gear and forcing air in)

It will spin the turbo by reving the engine, however my 21 turbo dumps its boost to Atmosphere (Chav, I know, but I love scaring people and old ladies on the Pavement ) It does however let me know that the turbo only spins when you really give the throttle a bootful, this is the only time that the dump valve will dump the boost. My dump valve has quite a soft spring in it meaning it does not take much boost pressure for this to happen.

IMO you will have to rev the engines nuts off to make it spin the turbo, a blip on the throttle will be of no consequence in helping to keep the turbo spinning.

I think if the turbo really suffers that much lag then you need to find away to make the turbo spin up faster, to be honest the 21 turbo has a bigger turbo than the GTA ; I dont really suffer any real lag it can be improved by improving the pipework and the housing that gets rid of the exhaust gases the quicker they exit, the quicker the turbo will spin up you want as little or no back pressure as possible .....a little ignition advance would not go amiss either, it works for a 21 turbo when intake temps are kept low.

Maybe a nice set of custom manifolds would make a difference?

I am currently obtaining a 4 branch equal length exhaust manifold for my 21 this will be coupled a bigger Cossie housing with a bigger better flowing exhaust housing coupled to a 3" down pipe the results should be pretty good. Craig Righton is currently running 13.2 1/4's consistently with a T34 Cossie Xhorst housing and 3"down pipe the manifold being as Renault designed it on standard management!

We shall see ?

The PRV may have 2 extra cylinders than the J7R, however basic tuning principles apply

Si21

avoiding lag by pressing the throttle a bit earlier than you would normally to compensate

si21

I think if the turbo really suffers that much lag then you need to find away to make the turbo spin up faster, to be honest the 21 turbo has a bigger turbo than the GTA ; I dont really suffer any real lag it can be improved by improving the pipework and the housing that gets rid of the exhaust gases the quicker they exit, the quicker the turbo will spin up you want as little or no back pressure as possible .....a little ignition advance would not go amiss either, it works for a 21 turbo when intake temps are kept low.

Is that really you Si?

Fitting a larger volume manifold and turbine housing will not decrease lag.
The only way of making the GTA have less lag, is to fit an even smaller turbo or manifold volume, but this will choke the engine even further.

The 21 does have a bigger turbo, but then it doesnt have 2ft either side of manifold pipe for the gasses to flow down first (and lose heat) before hitting the turbine wheel, and because of it being a V setup, the exhaust pulses are not one after another continously either from one head as with an in-line 4...You have a weak initial pulse from one bank, then the other, so the total exhaust energy doesnt really build up until the revs and load are at a sufficient level..

So, the priciples of tuning a V engine, are not the same as an inline..

surely if you drive the GTA while allways above 3500 revs, then the turbo is on boost and you have power at any moment all of the time ???

Surely no one expects power from a turbo car when not on-boost.

I just know some one will contracdict this generalisation for some good reason.

surely if you drive the GTA while allways above 3500 revs, then the turbo is on boost and you have power at any moment all of the time ???

Surely no one expects power from a turbo car when not on-boost.

I just know some one will contracdict this generalisation for some good reason.

In a way, the GTA isnt laggy, as it comes on full boost quite low, around 2500-2800, but it is all at once. The R21, comes on full boost at 3000-3500, later than the GTA, but it has some usable boost from 2000 upwards... thats the difference...

The problem with the GTA is just the transition between off boost and on boost..

..but, thats what makes the GTA feel impressive...

Surely no one expects power from a turbo car when not on-boost.

The problem with the 2.5 GTA, is if you run it without a turbo, it is sooo slow, nothing like a normally aspirated 2.5 V6. Modern turbo cars are designed to be good off boost, like a normal n/a car, then add the boost on top, but you notice how bad things like Subarus, Evo's are on fuel economy. You can't have both.

Back in the 80's, economy and torque was more important than outright power or revs, so Renault for instance, reduced the breathing ability of the cams on the 21 and GTA when turbo'd, by running far less overlap and lift, to get good midrange cruising torque and boost the fuel economy. Their thinking was that as they were pumping in air, they could afford to detune the engine for reliability and economy, whilst still being a higher performance model..

The A610 enigne is a more modern thinking, as without the turbo, the spec is identical to a normally aspirated Laguna V6, so off boost it drives nearly just like one.

The A610 enigne is a more modern thinking, as without the turbo, the spec is identical to a normally aspirated Laguna V6, so off boost it drives nearly just like one.

Yeah.... gutless!!!

Rob came over today to start pulling his new engine out of our Safrane, and I can say without hesitation that that pulled like a train compared to the Laguna I also have which is a wimp in wimps clothing, until you get up into the revs where it'd be under boost anyway. I'm note sure how it's measured but the cams in the Saf are 1mm larger from tip to base of lobe, than the Z7U, which means 2mm more lift on the valve.

Tony's is certainly a lot more progressive but this may well be more down to his moo-hooo-hoowge turbo than anything else.

(not making a point here Dave, just I have the "benefit" of having both high and low compression Z7X's at my disposal)