dholmes

I have just spoken to Performance Turbo Systems about their chip upgrade. They have a solder on chip that piggy-backs the ECU and a valve that increase boost to 16psi (I think) resulting in 35 - 45 BHP. All for 225 pounds. Obviously my warranty won't be worth the paper is written on and my insurance premium will increase, but I am still left wondering: where's the catch?
Has anyone got this product fitted ( or similar )?

Colin

I am very familiar with the PTS kit - part of my original boost experiments used their kit - have a look at my web-site for dyno figures with and without their conversion.
(http://www.force8.demon.co.uk/impreza/dyno1.htm)

I would also recommend getting a boost gauge fitted as their conversion prevents the ECU detecting overboost - i.e. if for some reason the bleed valve loosened itself or similar you would rapidly damage your engine. At least with a boost gauge you can keep an eye on the boost level. You may also want to check what petrol they recommend - personally I'd be a little wary of using not using 98 RON.
I believe the kit is the same as Superchips (but cheaper), and does represent comparatively good value for money (although I think all of these conversions are quite expensive for what they are).

Some things to bear in mind when considering ECU modifications are:
- Does the overboost cutout still work (at a raised level)?
- Does the anti-knock ignition retardation still work?
- What petrol grade will the engine run-on? (re: anti-knock / RON)
- Does the immobiliser still work?
- Does it plug into the standard loom with no wire cuts?
- How quickly and easily can it be removed (i.e. the car put back to standard)?
- Are there any obvious changes in the engine compartment? (i.e. would a dealer spot it!?)
- Is the boost level adjustable (and if appropriate - ignition timing)?
- If you believe in "ECU Reset", then what effect that will have when running a higher boost? (Not an optimal one in my opinion).
- Never believe the quoted power increase - it'll always be optimistic! Also "peak power" increase only represents part of the picture - what you really want to know is the torque curve throughout the rpm range.

The 35-45 bhp you mention is, in my opinion, optimistic. I found about 25 bhp (at the flywheel), but nevertheless this is quite noticeable as this improvement is available from 3,300 rpm upwards. (25 bhp at 3,300 rpm equals about 40lbft in torque - quite an improvement.)

dholmes

Thanks Colin for your useful points.
I called PTS with Colins questions and PTS were very honest and helpful. Listed below are their responses.

- Does the over boost cutout still work (at a raised level)?
NO - over boost cutout is disabled.
- Does the anti-knock ignition retardation still work?
YES
- What petrol grade will the engine run-on? (re: anti-knock / RON)
All but SUL recommended
- Does the immobiliser still work?
YES
- Does it plug into the standard loom with no wire cuts?
NO - One wire cut.
- How quickly and easily can it be removed (i.e. the car put back to standard)?
Unsolder the 4 wires from piggy-back chip to the ECU and rejoin the original wire that was cut.
- Are there any obvious changes in the engine compartment? (i.e. would a dealer spot it!?)
Yes they are detectable.
- Is the boost level adjustable (and if appropriate - ignition timing)?
Yes the fitted valve can be adjusted up or down, but PTS don't recommend this without upgrading other parts.

PTS said ( I'm not 100% sure of the figures ) that a standard Impreza's valve is 12PSi and the valve they fit is set at 16PSi. So effectively they've increase the boost pressure and disabled the ECU boost pressure cut out.
It sounds to me, that one should definitely fit a boost gauge if opting for the chip upgrade. The digital gauge offered by PTS is configurable so the over boost red light can be set to come on a the desired level.

This begs several questions from my untrained mind:
1. What is over boost and how is it recognised?
2. How / when does it occur?
3. Why does the previously mentioned valve not stop over boost?

Colin

"Overboost cutout" basically means the ECU detecting too higher boost level and cutting fuel to the injectors (resulting in the car rapidly slowing down!). It's a safety feature - mainly for the engine that is - as too higher boost will overheat the turbo and damage the engine. Before the engine blows up though the car will go like a rocket! It can occur for a variety of reasons - the most common being the turbo hosing becoming disconnected from the wastegate actuator or the wastegate solenoid etc. It is often recommended to uprate the turbo hosing - which is probably a good idea, although in experiments I've found the standard hosing to be better than it looks!

Overboost is determined by the ECU monitoring the voltage level from the MAP (Manifold Absolute Pressure) sensor. This sensor outputs a voltage proportional to pressure and if the voltage goes above a preset threshold, the ECU cuts the engine. Part of PTS' modification (and others) is in-line with this signal (from the sensor to the ECU) to stop the voltage rising above a certain level - and of course the downside is that the ECU can no longer sense too higher boost pressure. A more intelligent "chip" would re-map the MAP voltage output to provide engine cutout at a higher boost level - so the safety feature is still there.

In answer to your third question, the solenoid valve (fitted as standard) or the add-on valve are simply methods for controlling/creating more boost - and are irrelevant to how the ECU senses boost pressure.

Finally I must say that I also found PTS very friendly and helpful - much better than some of their competitors (mentioning no names)!