Sam's build thread

[sambb]

Nankang AR-1 R Spec tyre review

hang on - 1.75kg heavier but they are new 215 nankang vs old 205 Nitto so maybe not as heavy as I first thought

Whats the duro say for them Andrew? are yours treadwear 80?

[metalhead]

Thanks Sam, yeh, I'd read that thread before my decision. Duro readings were basically bang on 60 across the tyre. Pretty sure they're all 80 treadwear, mine were all manufactured in the last week of 2017, so nice and fresh. Paid $280/tyre for 295/30R18 fitted and balanced from a guy locally.

[Sydneykid]

Thanks Gary, I'm more than happy to share my thoughts and experiences with them, but really don't have any other R Spec experience to compare them with. Hopefully they'll be at least as fast as my street Continentals this time though!

Not expecting anything definitive, just tying to get feedback from guys running different sizes, weights of car and horsepower. I think there are a couple of categories looking at the AR1 as a control tyre because of the sharp prices on offer. I'll get feed back from Jordan, but a RWD, decent power car like your would add to the knowledge base.

For a control we don't care so much about how fast they are, since everyone is in the same boat. What is important is consistency, we don't want a huge "green tyre" advantage for example, or tyres that fall off the cliff after a few heat cycles. That's what makes a cheap tyre to buy a very expensive tyre to race on.

Where they rate grip wise, it's too early to say, not enough different cars, not enough laps, not enough time in the field. They do have plenty of competition, for example we ran Hankooks at the 6 Hour last year on the 335i (it was the control tyre) and we could have got through the whole race with just changing the front right. At lap times pretty much the same as the A050's. Previously we have run DZ03G's which are my go to tyre, they are just all round good at everything. So the AR1 won't have much room to fit in between them and the A050, if it's to be rated there.


Cheers
Gary

[Sydneykid]

Thanks Sam, yeh, I'd read that thread before my decision. Duro readings were basically bang on 60 across the tyre. Pretty sure they're all 80 treadwear, mine were all manufactured in the last week of 2017, so nice and fresh. Paid $280/tyre for 295/30R18 fitted and balanced from a guy locally.

Duro readings after a couple runs or at the end of the day would be useful, or when you get home and they are cold, thanks.

Cheers
Gary

[sambb]

curious to see what my A050 softs will measure as

[sambb]

So I've had to do a bit of fiddling to get the worked K03s turbo working properly. I initially installed it with the turbosmart 7psi spring and it never felt right and didn't feel like an improvement on the stock turbo/manifold. When I looked into it with VCDS logs the N75 duty cycle was all over the place. This wouldn't be such an issue if it was keeping the boost stable but you can see from the actual boost columns in the higher rev range that the boost was oscillating. I'm certain that the 7psi spring is too weak when the tiny little turbine is oversped (very easy in a K03s) and its trying to spill the excess boost out via a flapper that has a mind of its own - well that's my theory anyway.

So what I did was put in the 10psi spring into the turbosmart actuator. Basically it'll crack later which ordinarily would cause a steeper boost ramp but I've found that with these turbos they have a mind of their own anyway when it comes to spool and the increase in spring can barely be felt. Where it can be felt though is in the midrange and top end. The actuator can better resist the pressure on the back of the wastegate flap and is more likely to be positioned where the N75 tells it to go. The down side is that since the tunes N75 is written for a weaker spring it'll basically overboost unless you do something to clip the boost peak. Obviously you could alter N75 behaviour in the tune which hopefully i'll do down the track, but short term since I'm a week out from Bathurst I did it the mechanical way. Its hard to see from the pics but basically the N75 has been laid on its back rather than been fed from underneath via a long tub coming off the induction pipe. Prior to the N75 a tee piece taps off some of the air and bypasses it through a turbosmart MBC and then back into the line that goes to the wastegate. To set it up you open the MBC up which will put the boost peak onto spring pressure. You then progressively tighten it down until you start to see the boost rising and then be careful until you hit your desired peak. The tunes specified/expected/setpoint peak is about 1350mbar/1.35bar/20psi so I set the MBC for that. This MBC will actually vent the excess air (air it doesn't need to get the wastegate to do what I need it to do) to atmosphere. This is normally a no no with a MAF sensed car as its technically an air leak but it isn't a leak unless you are under boost (logs prove that with no corrections happening) and under boost the fuel logs I've done are bang on. I've found that if you use closed circuit series flow controllers, that the boost will hit the desired peak and then suddenly drop 5psi before stabilising. These MBC's (mine is a turbosmart) works perfectly - it'll peak at 1.35bar and then hold nice and flat which gives you a much better top end.

here's the result. No timing added in this picture but you can see that the actual boost is smooth and consistent - a bit under at the torque peak and a bit over throughout the higher rpm (will it is as of now at least). The N75 duty cycle is stable too because the tune thinks it is managing the N75 perfectly as the MAP sensor see's stable boost. In short the bypass allows a controlled amount of boost pressure that the N75 wasn't able to manage/wasn't able to get onto the actuator, to bypass the solenoid and get onto the actuator via a different path to help it out when needed.
I've started adding timing and am up to 7.5 extra degrees added. This engine doesn't seem to be timing limited. I have the same amount of slight timing pull at 6, 6.75 and 7.5 without much extra power being made. So I'm going to pull the timing back a touch and start increasing the boost up to the 1.42 bar specified max. I expect that it'll be boost limited in only a few little steps so then i'll find that sweet spot and go back to getting the right timing.
Just a thought on intercoolers. True story but my other stock engine with the same turbo/mani but with a standard side mount made nearly 20 g/s more than where I'm at now. The side mount had a boost actuated water spray and some pretty elaborate ducting and I was running a 45cc water injection nozzle pre throttle body but it hauled arse. I don't think there's anything wrong with the engine, I think its the intercooler causing pressure drop. To my mind if you have a K03s which is into overspeed territory very quickly it is saturated easily. I'm thinking that with a giant pressure dropping IC and a small trubo that if the turbo has to generate an extra 2psi to compensate for the IC pressure drop, it can only do this by spinning faster but if its already saturated then no more power can be made, just heat. I seriously think the seat sport IC is robbing me of power. Just my two cents but I think that a single pass IC with less pressure drop augmented with water spray or water injection is the way to go on small turbos. As it is I'm going to slowly accumulate parts for either a hybrid K03 or garret which might tale a while so I'll live with it and keep the big FMIC. Anyway its all fun. Its on about 175g/s peak atm but I still have boost and timing to fine tune so maybe it'll crack 180g/s if I'm lucky but it does feel really strong in the midrange with the 10psi spring.

[sambb]

Noooo Bathurst forecast shows 30 degree days with showers so I'm guessing storms. Won't watch any replays of the last laps of last years Bathurst 1000 or the 12hr between now and then or i'll loose my nerve! Andrew get a good heat cycle into those new AR-1's and scrub them good. We might have rivers coming down the esses at us on the start line.

[metalhead]

Hmmm... That might be enough to sway me to just run on my street tyres... I was debating about doing that anyway just because I know how the car responds on them, and Bathurst is intimidating enough without throwing a huge unknown like tyres into the mix. But my street Continentals are excellent in the rain, I've competed on them in wet events a few times, and the few things I've read about the Nankangs in heavy rain were not overly positive.

[sambb]

yeah the nankangs have hardly any tread cuts. They are very soft though. If its shiny wet or even light rain wet but without puddles they will be still better than a street tyre. It astonished me in the mud/wet at Tamworth last year how much grip the A050 softs had but they had a lot more tread depth then. I'm on the indicators on a couple of the tyres now so I'd be silly to expect the same of them. But you are right at a place like Bathurst in the wet most of your speed will come from confidence especially in a hillclimb. Do you have two sets of rims? and a trailer to fit them in? The report goes up to Saturday atm so tomorrow we'll know if sunday will be worse or not. Yeah I definitely wont worry about running front mediums now - softs it will be and if its typhoon weather I'll run my street Toyo R1R's. I haven't run in the wet since I added a whole 1/1/2 degrees of extra front camber and zero'd the rear toe so I'll be edgy too. I'm ok on the Esses day - last year (2nd time there) it was wet in the morning and I felt comfortable for once but day 2 Mountain straight always gets the pulse up. In contrast to day 1 I've never finished a run on day 2 without my hands shaking to be honest.
I like to get up there in the afternoon and get the car ready for the next day so that there was no rush before scrute the next day and went out on the road and just plied up and down the esses to really get it locked away in my head. Not fast cos it s a public road until morning but it really helped bank the lines for me to sleep on and I felt fine about it the next day. Even the esses is too far/step/long to be able to walk it in the morning unless you are a really early riser. For mountain straight though there's not much to learn from doing public road speeds the arvo before other than just seeing where the road goes cos when you are going three times as fast the next day everything you thought you'd do goes to sh&&t. But yeah if we get up there at a reasonable time on Friday arvo/evening we can go for a bit of a recce in my car first and it'll pay off the next day. Wet or dry its gonna be wicked.

[seangti]

hey mate, have you tried ME7 logger from nefmoto? I may have the zip file at home and can send you. I think it requires a different cable for logging to VCDS, mines just an ebay cable, I can confirm specifics if interested. ME7 Logger has much higher resolution (20hz) than VCDS's ~.9hz and can log many more fields at once...

I'm heading to Lakeside this weekend, haven't been out since November so will nice to open it up a bit.

[sambb]

I do have nefmoto but have only used it to load a tune. Havent logged with it because to be honest it looked like Arabic to me - the naming of all the columns etc and I'd put it in the too hard basket. But I'll get into it cos I'll probably have a play with my K03s and some pre turbo water injection before I jump into K03 hybrid territory. I need left foot brake, maybe linear throttle (but not sure about that) and would love to try a 2 step so i'll need to reacquaint with nefmoto to do all that too I suppose. Yesterday I upped the boost to 1.4bar and the thing came alive so Its liking boost more than timing. I'll get back into finding the timing threshold at that level when it dries out and then i'll be good to go.
Cool re getting back on the track. Its raining up your way too yeah. enjoy!

[seangti]

Yeah we had a wet back end of last week. Forecast is dry this week. Hoping for a dry weekend.

I have left foot braking enabled on my car, though had the tuner do it so no idea how to go about it first hand. I do like it with the diff, good to trim the line a bit when you're a little too hot mid corner.

[Sydneykid]

I think its the intercooler causing pressure drop. To my mind if you have a K03s which is into overspeed territory very quickly it is saturated easily. I'm thinking that with a giant pressure dropping IC and a small trubo that if the turbo has to generate an extra 2psi to compensate for the IC pressure drop, it can only do this by spinning faster but if its already saturated then no more power can be made, just heat. I seriously think the seat sport IC is robbing me of power. Just my two cents but I think that a single pass IC with less pressure drop augmented with water spray or water injection is the way to go on small turbos. As it is I'm going to slowly accumulate parts for either a hybrid K03 or garret which might tale a while so I'll live with it and keep the big FMIC.

High school physics Sam, Boyle's Law, do you remember it?

Keeping in mind that it's not the volume of air but the weight of it that determines an engine’s power output. Using the more recent combinations (temperature added) to Boyle's law, and some rough maths. Assuming that the intake air temp after the small intercooler is, say, 50 degrees and the intake air temp after the large intercooler is 30 degrees. Noting that the temperature used in the formula is absolute, hence add 273.

(273+50)/(273+30) = 1.066 so 6.6% increase.
1 bar = 14.5 psi
14.5 psi + 6.6% = 15.5 psi
So roughly dropping the intake temp 20C will have the same affect as adding 1 psi of boost to the weight of the air into the engine.

Then add the effects of the cooler inlet air on lessening detonation, which means more ignition advance can be used and lower exhaust gas temperature, all of which help power production.

More convincing?

Sorry there's still a little bit more of the rules of thermodynamics left to consider (ooops, more high school physics), the volume of air (in a confined space) is reflected in the pressure, which in our case equals boost. The volume of air changes when it is heated (or cooled) and I don't have a chart handy with 20 to 40 degrees, but I do have one for 22 to 43 degrees. If, say, 2 m3 of air is heated from 22 degrees to 43 degrees, then the volume correction factor is 1.08 and the new volume can be calculated as (2 m3) x 1.08 = 2.16 m3.

Using our small intercooler versus large intercooler temperature difference of 20 degrees that's around 8% less air pressure for the same volume. Hence 14.5 psi (small intercooler) would be 13.3 psi (large intercooler) because the air temperature is lower.

Net result, roughly gaining effectively 1 psi of boost due to weight and loosing roughly 1 psi of boost due to volume.

Any measurable difference greater than say 1 psi between the inlet air pressure into the intercooler and the inlet air pressure out of the intercooler would reflect its internal restriction to airflow. I'd also measure the inlet air temp in and out to give an idea of the efficiency of the intercooler. A really good air to air intercooler is around 75% efficient ie; it will drop the inlet air temp 75& of the difference between the compressor output air temp and the ambient air temp.

Something like, say;
100 degrees out of the compressor
30 degrees ambient
75% efficiency
= 100 - 30 = 70 x 75% = 52.5 degrees temperature drop across the intercooler
100 - 52.5 = 47.5 degrees out of the intercooler.


Hope you had fun with physics today?
Cheers
Gary

[Sydneykid]

I have left foot braking enabled on my car.

As I am sure you know, left foot braking is a band aid, simply covering up what the real problem is. Something like it needs more negative camber and/or caster on the front and more toe out on the rear. Properly set up, varying degrees of throttle lift should give you more than enough weight transfer control to mitigate any mid corner understeer.

Cheers
Gary

[sambb]

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.
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.