I've got a MY98 WRX with a Piper X induction kit, Magnex straight through centre and BB and (I believe) a big VF22 turbo as standard. It doesn't really pick up until about 3500 - 4000 rpm so what are the best ways to make the turbo spool up more quickly, except replacing it with a smaller one...? I know a down pipe will help quite a lot but just how much lower down would the turbo come in and will a dump valve or bleed valve or Dawes help the situation? Also, I guess a new ECU (Link, Motec etc) would increase spool up speed - how do they do that then?

[Edited by scoobysnacks - 3/12/2002 8:58:16 PM]

[Edited by scoobysnacks - 3/12/2002 11:03:46 PM]

My cat free down pipe has made the turbo spoolup about 500rpm earlier.

electronic boost controller...:D

scoobysnacks,
Various methods of improving turbo spool up time....

1. Full anti lag setup. Requires major £££ and is illegal to use on the road :(
2. Improve exhaust gas flow to the turbo by removing restrictions i.e. porting the head and manifold, replacing the downpipe etc
3. Fit a boost controller to make sure that you don't get any wastegate creep when aiming for your set boost level. Various ways of controlling the boost to do this, either electronically or mechanically (Dawes)
4. Modify the turbo and fit a smaller exhaust housing
5. Modify the turbo and fit a lighter titanium turbo blade
6. Modify the turbo to a ball bearing turbo. (I'm not sure if the VF series are BB or not as I don't know them that well)

Hope this helps

Andy

I think the vf22 is the biggest in the vf series & it is ball bearing.
What about a shot of NOS??http://www.stopstart.fsnet.co.uk/smilie/thinkerg.gif
Cheers
Justin ( lovin my vf24http://www.stopstart.fsnet.co.uk/smilie/rolleyes.gif )

What is wastegate creep???

AFAIK replacing the downpipe will be cheaper than all the above, plus to get the full benefit of other mods you'll need to change the DP anyway...... so just do it :D

I've got the Magnex centre (with resonator) and a SS DP - together these give a big boost in torque low dowdown.

Cheers
Tim

Dawes Device

Wastegate creep is your wastegate opening a little before your boost target is reached. All cars using the OE 2 port solenoid suffer from this - about .7bar on a my99/00 will see the wastegate open, your boost solenoid pulses to bleed air away from the wastegate to reach target....it obviously can't get it all.

Fitting a Dawes fixes this, and contributes to the quicker spool-up element of this mod.

Not sure how a 3-port solenoid (STi's) is plumbed - is the 3rd port the wastegate?

Richard

Dowser,
A 3 port solenoid is a very similar setup. It has 1 port for the inlet from the turbo, port 2 for the outlet to the actuator and port 3 for the bleed back to the intake.

All boost controllers allow some wastegate creep because that is how they control at the set level i.e. by opening slightly before you get to the desired boost so that you don't overshoot. Most cars can tolerate a slight amount of overshoot when setting the boost and so if you can keep the wastegate closed for longer then you will get a faster build up of boost but you may get a slight peak higher than what you want.

Andy

Thanks Andy

Does the actuator output on the 3-port see any air while target is being reached - on a 2-port set-up, between .7 and target will see creep. Is a 3-port capable of holding this off a bit longer, until target is almost reached (say, 1 bar) before it tries to stop overshoot? Never understood the difference between 2 & 3 ports, but always assumed this was why...

Richard
PS: Dawes doesn't allow any wastegate creep - it's closed until target is hit :)

I assume that this is how they work as well. I don't know for certain but I would have thought this is how they wil be able to reduce the amount of creep.

Andy

"Richard
PS: Dawes doesn't allow any wastegate creep - it's closed until target is hit "

It can Dowser if the bleed hole is enlarged in the elbow on the Dawes, open it out from .5 mm to 1.5 mm and back off the Dawes, this allows the Dawes to open earlier than target boost, then the bleed allows the target boost to be reached with the Dawes open, set like this you get some creep as the bleed is unable to completly lower the pressure in the WG actuator line when the Dawes is open.

Harry

Thanks Harry - you're right, of course. Similar to the 3-port design (it seems), it limits creep a lot more than the OE 2-port solenoid set-up.

Richard (with Dawes, 2mm bleed, and a little creep!)

A Dawes with no bleed still has a proportional element near to boost target. The ball is not either on its seat or off it, there is an equilibrium point.

Feeding the original 2 port solenoid the right duty cycle (ie 95% during spool up with the correct restrictor size and actuator tension) gives no more wastegate creep than a Dawes with no bleed or a disconnected wastegate that I can tell.

I don't think a Dawes with a VF22 is a sensible suggestion - it could hold the boost way beyond what your injectors might handle at the top end. Dawes will attempt to give you a flat boost curve until the actuator or flow makes it taper - likely to be little with such a big turbo on 2L engine.

How about a remap to optimise ignition timing low down?

John,

MY98 ECU sets duty-ratio to about 92% as soon as the throttle is touched, and until RPM > 3000, at which point it jumps to its closed-loop value.

I don't know yet whether the 3000 RPM is a hard limit, 'cos I've only looked into spool-up response a few times so far with my datalogger / boost controller.

I will try taking logs of slow acceleration, and deceleration to see how the spool-up mode of the ECU is activated / stopped.

Then a tighter actuator and/or different restrictor might give you less creep assuming a capable controller (ie not the ECU one!)

[Edited by john banks - 3/13/2002 5:17:43 PM]

Id suggest a twin dump down pipe as these contribute to better spool up (does on my car anyway and thats a scoobymania pipe ;))
This is the cheapest i know of and probably the best sounding too ;) its not too intrusive (unless you have a straight thru system) and the torque is on tap :D
Its a must have ;)

Tony:D

All the methods of reducing lag described above (except the turbo mods and ALS) will only give very MINOR changes.

What really would help is a stroker kit. And a modded turbo, cleaned, ported and clipped, better lighter blade, etc.

(To keep the turbo spinning between gear changes, you could also fit a good VTA BOV, if you havent already.)

None of these are cheap, of course.

Wow, I cant believe how well and objectively I answered this question. Especially since I normally talk BS in the OT sections.

Oh, wait: you could also buy a Mitsubishi Lancer Evolution 6 Tommi Mäkinen Edition (which has a titanium turbo), much less lag and probably the easiest and fastest way of getting rid of your laggy car. :p

Oh, can someone show me the WASTEGATE on a Scooby? Thanks.

(hint: there isnt one, dont bother looking for it)

Thanks for all the responses guys - I guess a new downpipe is the cheapest, easiest mod that'll make a reasonable difference then. However... if I want to remain road legal at all times or not have the hassle of swapping pipes come MOT time what would you recommend out of: 1) a new ECU, or 2) a new downpipe and high flow centre cat? I believe the costs for each option would be similar (£750 ish?) but what would be more effective on it's own? Obviously both would be best, but more than I'd be prepared to spend...
Edited to say that I guess I'm talking about power and torque increases now as well as low down turbo spool up.

[Edited by scoobysnacks - 3/13/2002 9:17:08 PM]

Claudius,
as you look the turbo from the front of the car, check for a cylindrically shaped box hanging on the top left part of your turbo. From the front side, the solenoid from the inlet is connected and from the back side you can see the rod which opens/shuts the wastegate on the back close to the downpipe.

That's an actuator.

How does a Scooby not have a wastegate Claudius? Not quite sure what you are getting at unless you are saying that it is internal rather than external, but it is still a wastegate?

[Edited by john banks - 3/14/2002 4:57:13 PM]