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Discussion Starter · #1 ·
Well, I popped my Aero on Power Engineering's rolling road today (same one as Bubbles was on last week) and the results were quite pleasing.

Before I went there, I fitted a brand new (but standard) dump valve. This is the modified one that Saab now sells, which can handle a bit more boost than the original.

Prompted by a discussion on plug gaps, I fitted brand new plugs gapped at 1.1mm just before I went there and brought another brand new set gapped at 0.9mm. From subjective experience when my car was still unmodified, I expected to see less low-down torque with the smaller gaps. The difference amazed me (and the operator), giving 15bhp more at the wheels with the smaller gaps and more torque over the entire range, typically 10-15lbft. Interesting. Perhaps there's a problem with my DI cassette and it can't handle big plug gaps under high boost?

Anyway, the first run produced a respectable 280hp (225hp at the wheels) and 314lbft torque. The second run with the smaller plug gaps gave 305hp (240hp at the wheels) with 330lbft torque. A third run confirmed this.

Here are the curves.


Comparing to Bubbles' plots last week, peak torque is around the same place - 3500RPM. However, the spread is wider, with over 310lbft available over the 2500-5000RPM range.

I expect this difference between the cars is just down to more boost and better fuelling as I am simply relying on the ECU, exhaust and air intake for the extra performance so the ECU is set up to expect this sort of hp. As far as I know, Bubbles has an ECU with more modest ambitions, with other bolt-ons to increase the power further. One thing they did mention is that on the 300+hp runs, the fuel leaned out a bit. Perhaps I need some new injectors and the software modified to suit. I know Maptun have done similar cars to mine with larger injectors, so a call to them might be in order in the future.

Now all I have to do is learn to drive it...
 

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Discussion Starter · #3 ·
A rolling road session is £45 + VAT, if they don't need to spend extra time fixing things. As it was, I got my "messing about" with the plugs for the all-in price. He didn't print off the earlier plot, though, but we compared it on the screen.

Tyres are expendable
 

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Well, blow me Bill- that's LARGE!! Bubbles bows down- nuff respec an all dat! What boost were/are you running?

Perhaps I'll be having to catch you then...
I suspect we'll discuss this more later, but I really must go and pack now...
 

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Discussion Starter · #6 ·
Well, as I said before, 80% driver, 20% car. Perhaps this might just help compensate a bit for my lack of experience on the track. Then again, it may be enough rope to hang myself with...


Leon, now we know why you enjoyed yourself so much while contributing to the inevitable demise of my gearbox.

[Edit] Oh, boost holds at 1.6 bar up until some pretty high-ish RPM (3500-4000?), and stays well above 1 bar forever
And I do need to make acceleration rather than tyre smoke
 

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Bill, roughly speaking ... where would the needle be on my boost gauge if boost was 1 bar? I know there's a certain amount of error as the dash boost gauge is only intended as a guide and cannot be treated as gospel.

I'd like to get my CD checked out as like Andrews Aero it's over performing for a standard spec car, I'm (carefully) optimistic of getting 240-250bhp out of it providing I have good fuel in it and I give it a few good runs before I take it for testing. I don't expect my boost to stabilise at 1bar though, with the standard ECU boost drops to around top of red by 3750rpm, it peaks at off top of scale at around 2800-2900rpm before it begins to drop off. What might that equate to in units of pressure?

I do need to get the rad sorted before I start any monkey business though.
 

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Nice figures, and no LSD?
Seems incredible that 0.02mm of spark plug gap gives 25hp at the flywheel. I've always re-gapped my 1.1mm plugs to 0.9mm but couldn't remember the reason: maybe that's it
300 horses, as far as I can remember thats a first on these boards.[/b]
Gassy was chuffed (clippety-clopp ) with his 248 on the road a little while ago. Not sure what that was at the flywheel: 310ish? (not wishing to rain on anyone's parade... )
 

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Discussion Starter · #12 ·
Yep, I only got a measly 240hp at the wheels
I never really have great confidence in calculated flywheel hp, probably because I never fully understood how they know th transmission losses, but the figure at the wheels seems a lot less disputable to me. I think 250 at the wheels would be a nice target. Might not make Gassy too happy, but you can't please everyone

I'm still not convinced a LSD is necessary at these modest (!) power levels, given good suspension and tyres. The standard diff does some useful things. If all goes well, perhaps I'll get a chance to try out Bubbles' LSD at the track day.
 

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Discussion Starter · #13 ·
Originally posted by Jason (1992 9000CD 2.3T):
[qb]where would the needle be on my boost gauge if boost was 1 bar?[/qb][/b]
Hard to say for certain, but I think you might be just a bit into the red.
 

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Discussion Starter · #16 ·
Originally posted by Andrew (wrighar):
[qb]I'm a little with a nasty drone now in 2nd on overrun in slow moving traffic.[/qb][/b]
A little what? Little bloke (like me?)

Anyway, I really don't need congratulating, as I've only really "bolted on" the Maptun Stage 2 Aero upgrade (ECU and exhaust) and modified my airbox a bit.

That's as far as making power goes anyway. Getting it onto the road and throwing it away when I want to slow down cost a bit extra
 

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Originally posted by BillJ:
[qb]I'm still not convinced a LSD is necessary at these modest (!) power levels, given good suspension and tyres. The standard diff does some useful things. If all goes well, perhaps I'll get a chance to try out Bubbles' LSD at the track day.[/qb][/b]
Believe me, it's not so much that it's necessary, it's just that it (proportionately) improves power out of corners more than the equivalent amount spent on suspension, tyre & wheels upgrades. I originally got it to sort wet traction but the real grin is using it hard out of corners in the dry. Goodbye understeer drift!

Mark
 

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Discussion Starter · #18 ·
So have you seen any disadvantages yet? I assume there must be times (e.g. going over a pot-hole) where losing traction on one wheel and not the other could produce some disconcerting results. There's a pot-hole on a local road that I always seem to hit with my left-hand wheel while powering out of a roundabout. I'd be worried that the LSD would swing me into the kerb under these conditions.

Do you get this effect, and does it do anything else strange that a standard diff wouldn't?
 
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