Sam's build thread

[sambb]

That's atw hp in your calcs yeah. With the hardware I'm choosing I think I'd be happy with 250 atw hp. I currently have a 3 bar FPR and can go to another OE 4 bar. ECS Tuning do a plug n play adjustable fuel pressure reg that goes straight into the factory rail, so I can definitely go to that if need be.

[Sydneykid]

Being able to adjust the A/F ratio (roughly) via the FPR is a help where the ECU tuning has limitations. For example, on the Stagea the ECU runs the engine but comms to the ECU for the auto gear box and the ATTESA ECU for the 4WD. So there are limitation built in to the ECU firmware to prevent overloading the gearbox etc, such as maximum injector duty cycles are various RPM points for torque limitation. I used the adj FPR so I don't exceed the duty cycle limits. Then tuned around that. Otherwise you get stuck at 180 4WKW, whereas I've maxed out the injectors (80%) at 220 4WKW without tripping the load limitations.


Cheers
Gary

[sambb]

ignition coil pack test (including VAG ones): https://www.youtube.com/watch?v=4d3nrBZjYKA

Surprised to see how well the R8 coils performed relative to other coils eg Yaris that have been getting a good rep lately (considering also how 'bad' a rep the VAG coils get). Might just hang onto them.

[miahill0991]

Still gathering all the needed information and will decide later for a plan or maybe just get an EXPERT.

[Sirocco20348]

That's atw hp in your calcs yeah. With the hardware I'm choosing I think I'd be happy with 250 atw hp. I currently have a 3 bar FPR and can go to another OE 4 bar. ECS Tuning do a plug n play adjustable fuel pressure reg that goes straight into the factory rail, so I can definitely go to that if need be.

GFB do a drop in FPR aswell and it accommodates a gauge into the unit. No regrets..



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[sambb]

Cool. I'll check that one out. thanks mate.

[sambb]

So now that tracking has gone quiet until probably march, I found some motivation to get under the back of the car and look at re-shimming the stub axles for more rear toe out and neg camber. While under there I ran a tape measure over my rear beam suspension points and when I crunched the numbers got a bit of a shock. Seems when I measured the beam a while back I over estimated the motion/leverage ratio.
I had the ratios at 0.8 so had gone with 8kg/mm (448Lb/in) springs expecting a wheel rate of 288 Lb/in. That on paper tied in nicely with my 7kg/mm (390lb/in) fronts which have a wheel rate of 318 Lb/in. Turns out though the rear beam ratios are more like 0.86 giving a rear wheel rate of 331lb/in which exceeds the front and if I'm honest is damn choppy to live with.
Now if I go to 7kg/mm (391lb/in) rear springs with 0.86 ratios I'll get a rear wheel rate of 290lb/in which would put things exactly where I THOUGHT they had been. Running as rear stiff as it had been hadn't been scary or anything. It wasn't snap oversteering, the rear would predictably float through the corners and would only really step out at places like the fish hook if I outbraked myself. However since I swapped out the whiteleine front bar and went back to the OE one, the car would have the sensation of perhaps lifting the inside rear too much and over loading the outside front despite the front having good angles. I don't really want to go back to the stiffer front bar as the OE bar has really helped with power down traction on corner exit and has been a net gain, but I cant help wondering if coming back on the rear spring rate from 8kg to 7kg rears might just get the wheel rates a bit 'squarer' around the car and help it not over load that outside front.
I have since tried the rear beam without the anti roll bar so just on stiffer springs alone and id say rough surface running is about 2% improved so I think I can conclude from that that the ride problems come from the springs not from the rear bar. It is a bit more on the nose like that during steady state cornering so I do think the bar needs to be on there and set to max stiff to help that inside rear unload.
Problem is MCA don't do 7kg/mm 150mm springs, they only jump down to 6kg/mm which I think is going too soft so I'll have to track down some 7's off another spring maker too which is a bugger because MCA's 100 buck for a pair deal is pretty good for when you are tuning things.

Just not sure if coming back a notch on the rear spring rate might be the answer cos on paper it is very rear stiff as is?

[Sydneykid]

Sounds like a bad idea to me Sam, since you are not experiencing extreme rear nervousness under brakes then the spring rate clearly isn't excessive. As I'm sure you aware, reducing the rear spring rate also affects the rear anti roll as the sway bar acts through the spring. So if you go down in the spring rate you will have to go up in the anti roll rate to compensate. Plus the softer spring rate will also mean more anti roll in total is required. Double whammy.

At the risk of repeating myself, I never rely on measuring leverage and movement ratios with a tape measure/steel rule. Maybe I'm just not very good at it, that's why I always measure them by articulating the suspension through its travel and measuring the actual movements of the wheel in comparison to the spring seat. Sure it takes longer but it reveals all sorts of unusual stuff, mostly non linear ratios.

If you are concerned with excessive weight transfer to the outside front then the best tuning is done with the rear roll centre, which in your case means ride height. Lowering the roll centre (and the ride height) decreases the diagonal weight transfer. As does increasing the anti roll but there is limit with that, lowering the roll centre gives you another option.

Cheers
Gary

[sambb]

yep sounded like a bad idea to me too. I was jst worried that if it was grossly over stiff at the rear, and given that I didnt want to up the front stiffness to meet that, I was wondering if softening off the rear to meet the front might work. But yep having driven it for a few days now without the anti roll bar (even with the 8kg springs) its a bit of a dog - on the nose everywhere, indirect to steer, not fun. Rear Anti roll bar is basically mandatory.
I think you are on the money with further roll centre lowering needed at the back. Thinking about it the car is perfect hammering up a hill but is exposed cornering on downhill sweepers - that downhill scenario would be the perfect example of diagonal weight transfer to the outside front yeah. Thats where I struggled at south circuit was coming out of the chicanes and then throwing it over that left hander crest down into the hard braking zone for the hairpin. That corner alone was responsible for me killing the shoulder on my outside front tyre no matter how I approached it if I was trying to be fast. I'm not going to be able to fit 215/50/15 on the back under the guard lip without pumping the guards if I go lower, so short term I think i'll stick to running 215/50/15 fronts and 205/50/15 rears and then I should be able to remove one of the rear spring perch collars and hopefully get those tyres to tuck under the lip at full compression and get it 8-10mm lower static.
And you are right it really was very driveable despite the rear stiffness and toe out and the fact that most of the time I was on cold rears that were only 195's, so yeah softer not the answer.
Going forward then, itll be lower the rear more, 2mm per side toe out and 2 degrees neg camber at the rear and just live with the uncomfortable 8kg rear spring ride. sorry kids!!
thankyou Sir

[Sydneykid]

I have a guard roller at home currently (just gave the Skyline a little more) if you haven't already rolled the lip up on the rear guards. The additional neg camber may well give you enough clearance., but if you need it, it's available. I have no idea how people drive FWD cars without a rear swaybar, it's the cheapest most effective handling upgrade.

Cheers
Gary