Sam's build thread

[sambb]

Actually that may be something to do with a fly by wire throttle because sometimes a slight lift not even done abruptly will behave as though you've slammed the throttle plate shut. Could be the tunes operation of the throttle plate on decreasing loads not necessarily doing what your foot is doing??

[seangti]

Everything's a compromise, though I like this article on left foot braking - Left Foot Braking – Chris Harris | FluxAuto

[Sydneykid]

So basically if I have to add 2 psi to compensate for the bigger IC's pressure drop I still have a net benefit in that temps are lower. The only thing though is the k03s is way out of its efficiency range at 1.4bar. To find that extra 2 psi means really over speeding it though which has its own downsides but the bearings in it are new so it should be right I suppose. That's partly why I want to do pre Comp water injection to try to shift the compressor map for a more efficient top end.

The better intercooling should result in less boost being needed to make the same horsepower due to the increased "weight" of the air.
The better intercooling should result in less boost being seen at the engine due to the decreased "volume" of the air.
Net, horsepower wise, you should be better off.

As I am sure you are aware boost is simply a measure of resistance to airflow and its actually the airflow itself that makes the power, not boost. My philosophy is to make as much power as possible at the lowest boost possible ie; remove the restrictions. To me lower boost is a good thing, as I only care about the horsepower. As a result I don't ever tune via the boost gauge, it just leads you up the garden path.

I don't know whether or not the larger intercooler has more pressure drop, I'd be surprised if it did. But the only way to be sure is to measure it, measure the pressure before and after the intercooler. Maybe there is a leak in he system and that's why you are seeing less boost than with the smaller intercooler. Try spraying some soapy water over the pipework, joints and intercooler and see if there are any bubbles.

Water injection is useful, but I'd probably use a mix of methanol and water. The methanol lowers the inlet air temp and the water lowers the combustion temp. I don't use it in circuit racing as we would have to carry the extra weight of water to last the race length. Wheras with a hillclimb you'd only need a couple of litres or so.

Cheers
Gary

[Sydneykid]

Re left foot brake I sometimes find it really hard to do throttle lifts without it really aggressively dropping its boost which upsets the car a bit. Maybe a stiffer divertet valve spring would make pressure dumps on slight lifts less abrupt... not sure.

My view is if we consistently need left foot braking to generate sufficient weight transfer to mitigate the understeer, then the chassis set up requires too much weight transfer. My approach would be to change the set up such that it responds better to slight throttle changes.

I always find that it's tricky to set up the boost retention so that a small throttle lift doesn't dump too much boost to atmosphere. At the same time we also want to avoid reverse air flow, which firstly means locating the blow off valve as close to the throttle body as possible. Rule of thumb, I start of with a spring in the blow off valve that retains around half of the maximum boost. So if I'm running, say, 20 psi max boost then I want to retain around 10 psi in the inlet system. If the ECU allows I also dump a bit of extra fuel into the engine on slight throttle lifts and also retard the ignition ie; anti lag. It takes a bit of fine tuning on the track and can be hard on the turbo, especially one that is not designed for anti lag.

With the drive by wire throttle systems in the Audi and the Porsche it was possible to have linear response on increasing throttle whilst having non linear response on decreasing throttle. But again that requires a lot of on track tuning as it's not possible to duplicate on the dyno, well not without an F1 simulator budget anyway.


Cheers
Gary

[Sydneykid]

Everything's a compromise, though I like this article on left foot braking - Left Foot Braking – Chris Harris | FluxAuto

The trick is finding the least compromise

I have read that article or something similar before, the problem is is mixes the disciplines of circuit racing and rallying plus confuses trail braking to the apex with mid corner stabs on the brake pedal in an attempt to alleviate the understeer. Coming from karting, many of the drivers I work with trail brake on turn in, towards the apex, and then apply as much throttle as possible as early as possible for a faster exit. In a FWD car there is very little if any time spent transitioning from trail braking to acceleration, ie; there's not a lot of "mid corner". Plus any mid corner weight transfer off the front end is controlled by the rebound damper rates in the front, the rear swaybar and the bump damper rates in the rear.

The problem I have with the hand brake analogy is that we typically run around 95/15 front to rear brake bias in a FWD car, so there's not a lot of (ie; next to zero) effect on the rear wheels' slip angle from left foot braking. Similarly with the wheel spin, if it's spinning the inside wheel then fix the diff.

With the chassis set up properly we shouldn't need to mitigate understeer because there shouldn't be any.


Cheers
Gary

[sambb]

Must admit I don't know the pressure drop of the SEAT sport fmic. All I know is that guy Harding did a test years back on the stock side mount versus the forge fmic and the forge was very restrictive. The seat sport I have is meant to be a less restrictive design than the forge but ultimately is the same double pass type so I can only assume it may be worse than the stock smic. It's easily a meter and a half more pipework to fill with it. I guess also it's not apples versus her apples because the other setup used water injection which helped it run more timing. I'm thinking there was stuff all pressure drop so the turbo was closer to its comp efficiency island , flow was high, yet temps were low due to the water and knock prevention was way up. After a hard run the plenum used to be actually chilly to touch sometimes.
Interesting what you said re the 10psi drop from 20psi on a small lift. I'll keep an eye on it. I do have a stiffer spring I can throw in if need be. Tell you what a k03s with the unmuffled comp housing after I straight piped it is a noisy thing. DV action plus Comp surge is pretty dam loud and unavoidable being such s small turbo.
Sick today do spent the afternoon picking rubber pickup gum balls out of the tread cuts in my softs. Lots of them were blocked completely. I'm pretty anal like that but if I'm going to be confident to go hard in the wet then I need to know I've crossed that off. Fingers hurt now though!!

[Sydneykid]

Must admit I don't know the pressure drop of the SEAT sport fmic. All I know is that guy Harding did a test years back on the stock side mount versus the forge fmic and the forge was very restrictive. The seat sport I have is meant to be a less restrictive design than the forge but ultimately is the same double pass type so I can only assume it may be worse than the stock smic. It's easily a meter and a half more pipework to fill with it. I guess also it's not apples versus her apples because the other setup used water injection which helped it run more timing. I'm thinking there was stuff all pressure drop so the turbo was closer to its comp efficiency island , flow was high, yet temps were low due to the water and knock prevention was way up. After a hard run the plenum used to be actually chilly to touch sometimes.
Interesting what you said re the 10psi drop from 20psi on a small lift. I'll keep an eye on it. I do have a stiffer spring I can throw in if need be. Tell you what a k03s with the unmuffled comp housing after I straight piped it is a noisy thing. DV action plus Comp surge is pretty dam loud and unavoidable being such s small turbo.
Sick today do spent the afternoon picking rubber pickup gum balls out of the tread cuts in my softs. Lots of them were blocked completely. I'm pretty anal like that but if I'm going to be confident to go hard in the wet then I need to know I've crossed that off. Fingers hurt now though!!

The 20 versus 10 psi is a "rule of thumb" thing, a place to start. It has to be high enough pressure so that when you crack the throttle open it doesn't go to vacuum, because then you get the nothing ......... nothing ............ woooo hang on tight. Which just makes the driving on the limit rather tricky. But it has to be low enough pressure so the airflow doesn't reverse direction, which is bad for the lag but also not good for the turbo. Unfortunately that means trial and error.

I guess VW installed the muffler in the comp housing for a reason.

Whenever I am using a "new" intercooler I always check the airflow resistance and the cooling efficiency, some of them are terrible at one and good at the other. It's hard to actually find one that is good for both.

Without water injection you really are comparing apples and oranges. Inlet manifolds, even in a hot engine bay, can get very cold even without water injection. In winter on top of the mountain at Bathurst, on damp mornings, I've had Webers (yes, I am that old) freeze the butterflies. That for sure get's one's interest. Even with a Holley on top of a V8 I have had ice in the venturies at Philip Island.


Cheers
Gary

[sambb]

Yep muffler definitely muffled when it was there. But it would have been a flow mangler so its gone. My wife backed it up the driveway the other day and lifted off and after the ch ch ch ch she just looked at me and said 'what have you done to it now'. I just feined ignorance but she wasn't buying it.
Did a test of the DV and did a little kid corner lift. Boost went from 1.4bar down to 0.5 bar on the gauge. When I got home I pulled it apart and unfortunately I have the medium spring fitted and my spare is the soft. The hard cracks at between -19 to -24in/hg so will probably be more appropriate. I thought about washering it to give it a bit if preload but didn't have anything to fit. So what I did was change the DV orientation so that the boosted air is pushing into the side of the piston in the hope that it'll need a tad more of a pull from the diaphragm to get it open since boost won't be additive with the diaphragm signal in this orientation.
I'll have to see if there are any throttle body inlet pipes that have DV ports on them because I really do see what you are saying re dropping the boost at the throttle plate rather than through the entire length of the induction system. Keen to try that.

[Sydneykid]

Yep muffler definitely muffled when it was there. But it would have been a flow mangler so its gone. My wife backed it up the driveway the other day and lifted off and after the ch ch ch ch she just looked at me and said 'what have you done to it now'. I just feined ignorance but she wasn't buying it.

I've learnt to own up first, they have a knack of catching on especially after 30 years of experience.

Did a test of the DV and did a little kid corner lift. Boost went from 1.4bar down to 0.5 bar on the gauge. When I got home I pulled it apart and unfortunately I have the medium spring fitted and my spare is the soft. The hard cracks at between -19 to -24in/hg so will probably be more appropriate. I thought about washering it to give it a bit if preload but didn't have anything to fit. So what I did was change the DV orientation so that the boosted air is pushing into the side of the piston in the hope that it'll need a tad more of a pull from the diaphragm to get it open since boost won't be additive with the diaphragm signal in this orientation.

Worth a try, when I was first playing around with turbo cars for myself and my son we tried all sorts of things, dispelled a few myths and found quite a lot of "givens" were not only illogical but were just flat out wrong. Air flow (like aerodynamics) is still more trial and error for me than mathematical calculations. For adjusting blow off valves I originally had a number of discs that I cut from 1.5 mm thick aluminium sheet, shims, that I would stack up until I achieved the desired result. Once I achieved that I'd make up one shim and replace the stack. On the Skyline I have 2 HKS blow of valves, it needs a lot of venting, and I still haven't got them set up exactly as I want.

I'll have to see if there are any throttle body inlet pipes that have DV ports on them because I really do see what you are saying re dropping the boost at the throttle plate rather than through the entire length of the induction system. Keen to try that.

It's simple aerodynamics, rule #1 keep the airflow going in the same direction.



I used to use off the shelf adaptors, like these, from GCG I think. Just choose one that fits the rubber hose and cut out a section.



Cheers
Gary

[sambb]

re the diverter valve yep that's exactly what I was thinking I'd have to do. I'll see what GCG have and if there's nothing to suit ill get some straight pipe welded up.

Gary I'm a bit unsure about what pressure to set the 195/55/15 A050 softs for Bathurst. I've never run them on the new suspension/angles. Lateral G's will go up so despite the extra camber I'm thinking I should start them at 30psi to try to keep the tall profile a bit more rigid than running them down at 28psi on the old setup. thoughts?
If its dry on day 2 for mountain straight (depending on how day 1 goes) I may bump up the front bar to hard and follow that at the rear for the more drawn out corners. I never got to try that at Wakefield but surely its worth a shot to stiffen the whole car for the Reid - Macphillamy Pk sectin.

[sambb]

Andrew Andrew bring those AR-1's. They just updated the weather and they are saying 30/31 degrees both days mostly sunny.. No rain forecast yay!!!

[Sydneykid]

re the diverter valve yep that's exactly what I was thinking I'd have to do. I'll see what GCG have and if there's nothing to suit ill get some straight pipe welded up.

Gary I'm a bit unsure about what pressure to set the 195/55/15 A050 softs for Bathurst. I've never run them on the new suspension/angles. Lateral G's will go up so despite the extra camber I'm thinking I should start them at 30psi to try to keep the tall profile a bit more rigid than running them down at 28psi on the old setup. thoughts?
If its dry on day 2 for mountain straight (depending on how day 1 goes) I may bump up the front bar to hard and follow that at the rear for the more drawn out corners. I never got to try that at Wakefield but surely its worth a shot to stiffen the whole car for the Reid - Macphillamy Pk sectin.

The recommended target how pressure for A050's is ~31 psi, that's what I've the best success with as well. That's pretty easy for circuit racing, I have a data base for most circuits and most ambient temperatures which means I have a cold starting pressure that should end up at 31 psi after a couple of laps and not continue to build. Plus we have driver adj swaybars so we can temper the manic FWD cold tyre oversteer for the first race lap or so. In hillclimbs you don't have that luxury, so it's a bit of trial and error plus constant adjustment during the day. My suggestion would be to start off for the first run at say 30 psi in the rear and say 28 psi in the front. Then measure it straight away at the end of the run. You should be able to get 2 or 3 psi climb with front burn out etc, maybe 1 or 2 psi with the rear G force loading. If they are over 31 psi then I'd let them down, if they are under pump them up. For the next run, they should be still a bit warm, especially if it's 30 degrees, so you may not have to touch them. Just keep checking before and after each run and adjust accordingly.

I agree, I'd run a bit more anti roll and maybe a bit more damping for the Mt Straight runs. I suspect you may end up chasing tyre pressure all day there.

Have fun
Cheers
Gary

[sambb]

argh got your message too late Gary - think I was close anyway. On the Esses I was starting front 29 back 30 and was ending up at 30/1/2psi all round (inc a tyre warm) and in mountain straight I was starting at 28 front 29 rear and was finishing just under 31psi all round.

Was an awesome weekend. Despite slowwwww times from the whole field (like 3 seconds slower for an esses run????) where everyone except the club was certain there was a timing error, I can guarantee that not a single PB or record fell. So if you put times out of the picture and just look at the standings then I know the car was amazing compared to where it had been. Against the exact same top 10 opposition as last year in road reg >2.5L where I finished 6th at the Esses and 13th on Mountain straight, I improved to 4th at the Esses and 5th!!!! on Mountain Straight.
Mountain Straight was where I could really feel the car doing its thing. It was planted on the softs without any scary sideways action going into Griifins which was my big fear and gave me a hell of a lot more confidence from Reid to Mcphillamy. Against a field of atmo/cammed/blown V8's I was pretty consistently 4th fastest on the first split which means the turbo swap was worth it because that takes in the straight, Griffins and the run up to the cutting, but also says I was getting through Griffins faster than them for sure. One of the marshals had a radar gun the first year I was there so wish I knew what the griffins apex speeds were but I had to have been going quicker than them there given the horsepower defecit. I finally cracked how to line up the crest before you drop down the other side towards the grate. I'm not saying I was where I needed to be each time or that I wasn't chickening out on the throttle half the time but I knew where I needed to be and got it rightish on the last run. I still could go quicker of course but that's just hillclimbing - you get 4 looks at it all day on cold tyres so your never going to nail it.

So Gary super happy with the suspension. I definitely see that 3 degrees front neg whilst enough for the esses could have gone out to 3.5 for mountain straight. Now that the cars front:rear roll distribution is working the rears more equitably it was interesting to actually see consistent wear on all 4 tyres rather than seeing chundered fronts and no pressure rise in the rears. I was running 3mm toe out on the front and to be honest it didn't worry me at all and the zero toe at the back gave no surprises so I'm pretty happy to go to 2mm rear toe and take the rear camber out to 2 degrees neg now for sure. I didn't go up on the bars for mountain straight or even the dampers. The car felt very consistent and all the time was going to be in me just growing a pair really so I left it alone and just concentrated on not repeating mistakes and on resisting the urge to back out of it.
Got lots of vids but it'll me a bit to get them up.

[sambb]

Andrew did you get the email. They just sent one out admitting that the timing was out. What ****s me is they had people telling them with logs/video time stamps etc on day 1 that it was out and they just waved everyone away and let day 2 happen the same. They even told us they'd tested it on day 1 which they clearly hadn't because now they say they tested it and it was out. Apparently placings and relative times between everyone are correct and were consistent across the days which suggests a timing offset was thrown onto everyones times on split 1 like we all suspected. I've responded and asked if they can at least tell us what the suspected offset is so we can get an idea of what our real times would have looked like. Pete went feral at them and wants his money back.

[simon k]

sounds fantastic - I've been digging through lots of your threads - you're a legend for publishing all of this stuff!

DIY adjustable camber ball joints mod

My first sprint (DECA Wodonga) with the Polo is this weekend, it'll be stock with miserably bad "blacklion" tyres so the only way is up. A mate and I messed around a rear bar stiffener on Saturday between jobs on another car, but it was too hot and I was exhausted, maybe I'll do something with it this week. Otherwise the only thing I've done is disable the throttle cut on left-foot braking... at least I can only make improvements

question for you - you run wheel spacers (I think), but have you thought about some spacers behind the stub axles instead?