Icing on the cake...

As you know my G60 has come on well over the years (now a 1.9 and running 246bhp/222lbft on Stealths rollers), and I'm wondering now what next. I still plan on going down the nitrous route, but I'm wondering what I can do to get more out of the system, in everyday use, while keeping the spirit of the G60 (i.e not going turbo). I've had a few thoughts and would appreciate any comments.

Exhaust system I'm currently running a 4 branch manifold, but the exhaust system is a Longlife Stainless one, which to be honest is not a very good design (non mandel bends, small diameters etc.) presumably this is one area to address. Expected gains - presumably relatively small, however it's more free flowing, this will lead to lower temps and potentially more advance.

ISV Something Vince noticed was that my ISV was leaking slightly throughout the rev range - when we clamped the outlet pipe the boost pressure went up by about 1psi throughout the rev range. Is this indicative of a knackered/dirty ISV?

Pulley size/injectors I'm running a 68mm pulley at the moment, and my injectors are at around 90% (running 315's). That was on the 3 bar fuel pressure reg. I have now fitted a 3.5 bar one. This presumably gives me some breathing space but not enough to cope with the move to a 65mm pulley. So to go 65mm I'd need new injectors. Whats the next size up that would be suitable?

You got a vernier on the cam? Might be worth seeing what dialing the cam round a few degrees might do? Getting your engine spec in Desktop Dyno may help with that too...

What bore is the exhaust that is on there?

Worth cleaning the ISV at the very least, maybe source a new one next.

Nothing wrong with putting bigger injectors on. 440ccs are the way forward

im running 440s. 65mm would be a good choice for more lower down power, boost comes in earlier but you want a 2.5" system

And why dont you get 1 of those gyro valves?

With the bigger injectors, it seems like a huge increase to go from 315 to 440. Does it no sacrifice the low end accuracy by going so large? Is there anything inbetween (360ish for example)?

Bore size of the exhaust - I need to get under there with my calipers and check, but it's low. Can't imagine it's more than 2 inches.

Doh, forgotten I do have the vernier on there, so thats something to try.

As for the gyro valve, doesn't that interfer with the normal ISV operation of venting the boost if it detecting pinking? Don't really want to be compromising something keeping my engine healthy.

personally I wouldn't just stick bigger injectors on there without a remap.

dirtytorque wrote:personally I wouldn't just stick bigger injectors on there without a remap.

Oh, don't worry that wasn't the plan, if it's new injectors, it'll definately be with a remap...

jmc wrote:

dirtytorque wrote:personally I wouldn't just stick bigger injectors on there without a remap.

Oh, don't worry that wasn't the plan, if it's new injectors, it'll definately be with a remap...

cool,well then the bigger injectors won't affect your bottom end power because the ecu will still have the same target afr's it will just adjust the injector open times to allow for the increased flow rate and help your duty cycle situation at the other end.

If your engine flows well, your isv wont see 1 bar to open to bleed off.
Im not running an isv and my boost gauge never goes over 10psi.

I'd recommend a one way valve on your ISV, a 2.5" exhaust and a 50 shot of nitrous!!

So it looks like we have a plan....

Decent exhaust 1st off.

Then bigger injectors, 65mm pulley, ISV check valve, and a remap. Along with my nitrous of course ;-)

There is a guy in america who cuts open the intake ans ports it to flow around 25% more and then welds it back up costs $300. Might be worth considering.

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Probably have to have it port matched on arrival from the US to your head. Speak to JP on here!

Hmm, good find. I'll drop that guy and email CTW - intrigued to see what he can do for that

Got some details from ScientificRabbit on his ported inlet manifolds. After talking with JNL, I'm goin to hang off from that at the moment.

However was talking with JP Exhausts this morning about a custom 2.5" exhaust, so that should be on the cards

jmc wrote:Got some details from ScientificRabbit on his ported inlet manifolds. After talking with JNL, I'm goin to hang off from that at the moment.

However was talking with JP Exhausts this morning about a custom 2.5" exhaust, so that should be on the cards

Would you care to expand on the reasons for your choices? In the interests of boredom relief!

Was looking at the guys method of measuring airflow increase. He was literally doing it on pressure drop which is a linear scale. Airflow is measured on an incline manometer which has a parabolic curve to it so although there is a 10-25% pressure drop you may find there is no flow increase or only a minimal 3-4% depending where on the curve the flow is.

This is then further backed up by the massive drop in bottom end power with no real top end gain and only a little upper mid range. So area under the curve is worse indicating the runners have been made too big.

With regards to the exhaust it sounds like the existing exhaust system has bottle necks in it. Supercharged motors need good exhaust flow to reduce back pressure, allowing more fresh air charge, dropping EGT's subsequently allowing for more ignition advance = more power. Even if there is no significant initial power gain other than smoother throttle response the other additions at a later date of smaller pulley etc will really benefit from it.

Thanks JP

Glad I didn't buy one then. It will be interesting to see what a standard intake flows when plumbed into an accurate flow bench.

Here's something to give you guys a laugh. Just been under the car and taken some measurements off my current exhaust system as I'm wanting to go to a 2.5" inch one, and I had a gut feeling my current one is a tad restrictive for my setup.

For some reason (and I've only just realised this having never thought about it before) my car has a 4 box system - 2 down the centre, then one at the right angle and one before the tail pipe. Is this really odd?

Anyway, on with the pipe diameter measurements...

Before 1st box (just after decat) 57.6mm
Between 1st and 2nd box 57.2mm
After 2nd box 53mm
Before 3rd box 49mm
After 3rd box 47mm
After 4th box 50mm

Now, I'm assuming 2.5" is bore size (JP talked about 63mm bore which sounds about right), and these are external measures. So on a scale of 1-10 how crappy is mine

Lol I know you said it was restrictive in places but you just took it to a whole new level 2.5" system with 2 straight thru box's will work you a treat without making too much noise.

jmc wrote:Here's something to give you guys a laugh. Just been under the car and taken some measurements off my current exhaust system as I'm wanting to go to a 2.5" inch one, and I had a gut feeling my current one is a tad restrictive for my setup.

For some reason (and I've only just realised this having never thought about it before) my car has a 4 box system - 2 down the centre, then one at the right angle and one before the tail pipe. Is this really odd?

Anyway, on with the pipe diameter measurements...

Before 1st box (just after decat) 57.6mm
Between 1st and 2nd box 57.2mm
After 2nd box 53mm
Before 3rd box 49mm
After 3rd box 47mm
After 4th box 50mm

Now, I'm assuming 2.5" is bore size (JP talked about 63mm bore which sounds about right), and these are external measures. So on a scale of 1-10 how crappy is mine

is that the standard exhaust setup?

My current one is a Longlife stainless steel aftermarket jobbie fitted by the previous owner. They may have modelled it one the standard one - but to be honest I've never seen a standard one so wouldn't know

Cool,well i'll be taking mine off soon so i'll measure it up out of curiosity.
I think mine is stock.

standard is 2 1/4

Well, I've gone and booked myself in with JP Exhausts for the 8th April. Rick there had a laugh when I told him that the current one I have went down to 47mm at one point . Also bought the 440's from Adie , just have to be on the look out for a 65mm pulley now.

What about the phenolic spacers for the inlet manifold - worth it on a G60 where the inlet is directly above the exhaust? I would have thought a lot of the heat would come from convention, rather than conduction.

you should have plenty of fuel! mine idled loverly on those injectors, spot on 800, was told bigger injectors cause lumpy idle? even saw 32mpg on 20min drive