DDMotorsports Redline Time Attack Round #2 Results!
 

Well round #2 of the 2009 Redline Time Attack series is in the books and this marks the halfway point in the season for the Street RWD West class and the DDMotorsports Project 370Z.

Unlike most teams, we are not out there this year to win these events. This year is a development year for the 370Z and our efforts with it in time attack. The main goal for this season of racing is to develop and test products for companies and see what the 370Z is capable of as a track car.

Round #1 of the series was at Buttonwillow Raceway and the car was very close to stock. At this event we did initial testing on the Mishimoto Oil Cooler kit, BC Racing ER Type coilovers, Hawk HP+ brake pads, Berk Technology High Flow Cats, SPL Parts rear camber arms and JWT Pop-Charger intakes. The rest of the car was stock. The track was technical with a lot of different types of turns ranging from low to somewhat high speed. All of the parts worked excellent with the exception of the stock limited slip differential, which as it turns out, broke at this event.

Round #2 was at Willow Springs Raceway and in contrast to Buttonwillow, this track has no low speed corners and a few long fast sweepers which really tell the tale of how your car is setup handling wise. Not to mention it was about 35 degrees hotter than it was at Buttonwillow. Between round #1 and round #2 we changed the stock wheels & tires to Forgestar F14 wheels and NT05 tires in the same size as the stock sport package wheels/tires. We also added a GTSPEC 4-point ladder brace, Nismo 60mm wheel studs, and lighter Muteki lug nuts. The rest of the car remained un-changed since Buttonwillow, including the damaged stock limited slip differential which we unfortunately did not have time to replace.

The Good:

BC Racing ER Type Coilovers – Between Buttonwillow and Willow Springs I have now tested these coilovers on virtually every type of turn imaginable. Once I got the compression and rebound set to where I was happy, the coilovers continued to impress me. I absolutely loved being able to adjust the compression and rebound separately, especially since some of the turns on this track are very high speed and a little bumpy, so the last thing I want is a car that gets upset over bumps at 125mph mid-corner.

Nitto NT05 Tires – These tires are a large leap above the stock Bridgestones when it comes to grip! They were very predictable and surprisingly sticky for a stock tire. I ran the stock widths, with a little shorter sidewalls and it was a world of difference compared to the stockers. These are my new favorite street tire for the track.

GTSPEC Ladder Brace – This little piece actually made a noticeable difference! Turn-in felt more crisp and precise due to the lack of flex in the front end. I am sure it would be even more noticeable on a track with tighter transitions.

The Bad:

Hawk HP+ Brake Pads – These pads worked fine at Buttonwillow and on every braking zone at Willow Springs, except for one. The braking zone going into turn 1 you are coming down from around 140mph and it seemed that the pads couldn’t handle hard braking from those speeds for that amount of time. Initial bite was good, but then the pads would quickly fall off and felt like a sort of glazing effect. I knew it wouldn’t be long before the car was too much for a street/track pad, but surprised that the Hawk HP+ worked as well as they did. Time for some real track pads though now that the car is getting faster.

Broken OEM LSD – So this must have happened at Buttonwillow and I am not really 100% sure what part broke but as I was changing the diff oil before the even a large piece of broken something came out of the drain plug. The diff oil smelled extremely burnt as well. The car drove ok on the street, but on the track it felt like an open diff in spots. I am just happy that the diff didn’t self destruct and lock up the wheels on me. We will find out more about what happened to the OEM VLSD soon once I swap it out for a Carbonetic 1.5 way LSD. A diff cooler will also be added soon to protect it.

Power Steering Boil – Apparently an upgraded power steering oil cooler will be needed as well. After each session I noticed the power steering fluid literally boiling in the reservoir. The steering felt fine and consistent while on track but boiling fluid can’t be good. I am glad now that I am not running a wider tire up front. Larger power steering oil cooler will be added soon.

Fuel Starvation – This one upsets me more than any other issue. Turn #2 is a long banked sweeper that generates a lot of lateral load on the car and during practice I experienced fuel starvation coming out of this corner. The throttle would be cut and SRM would not work anymore. The car would coast for probably 10-15 seconds (or up until the top of the balcony for those familiar with the track) and then the throttle and SRM would come back and everything would be find. This happened with ¼ tank of gas in practice and then again in the second time attack session with a little less than ½ tank. This is the only turn it happened in, and it did not happen at all at Buttonwillow, but the high g-loads for that extended period of time did result in fuel starvation. Although at this point it would be fine at most tracks, as we develop the car into a better handling machine producing higher lateral g-forces this problem will become more and more of an issue. The easy and free solution is to run more fuel, but that is not an ideal situation with the added weight.

Mishimoto Oil Cooler – Unfortunately I have found the limit of the Mishimoto Oil Cooler kit this past weekend. With air temps in the low 90s and a track with A LOT of wide open throttle/high sustained rpms I knew that if the oil cooler could keep the oil temp in check under these conditions then it could last through anything. Unfortunately after about 2 ½ laps of driving as hard as I possibly could, the oil temp hit 270 degrees. Time for a bigger core. I still think that for the price this oil cooler kit is perfect for most everybody, with the exception of the hardcore track junky who will do track days in 90+ degree weather.

No negative camber up front – This was my biggest lap time killer this past weekend. All of my front suspension linkage is still stock so I could not get more than the -1.7 degrees camber gained from lowering the car. With the long fast sweepers at this track, the understeer was rampant and the outer edge of the tires were doing all of the work. The front tires were fast for about 1 ½ laps of hard driving before they would start falling off. Bear in mind this would happen to any tire without the proper camber settings. I will continue to try and wait for SPL Parts front camber arms, but if they are not going to be done before the next event I suppose I will have to go with the SPC arms.

Well our goal was to learn a lot about the car and that we did. Our quickest time of the weekend was a 1:37.286 which was good for 7th place in the Street RWD class, about 3.5 seconds off of finishing on the podium. Given the circumstances I am again very happy with the results and really think that the 370Z can be a competitive platform in the Street RWD class. Bear in mind that our 370Z fits well within the rules of the new Stock RWD class. If we had entered that class we would have won by 3 seconds. The Stock class is a new addition to the Redline Time Attack season which debuted at this Round #2 event. The reason we didn’t switch to Stock RWD is because we wanted to keep our Street RWD points from Round #1 and also I don’t want to have to worry about keeping within the Stock RWD class rules for the rest of the year. So despite a 7th place finish I am very excited about the potential of this car and this team down the road. If the car’s development keeps going the way it is, hopefully we can make a run at the Street RWD class title in 2010 :D.

For those following the points chase, Round #2 marks the halfway point for the Western division Street Class. With two more events to go before a Street RWD West champion is decided, the DoubleDownMotorsports.com Project 370Z sits in a 3-way tie for 6th place in points, 37 points away from the leader.

Final Standings: Street RWD
1st - Jeremy Croiset - Berk Technology Toyota MR2 - 1:32.399
2nd - Robert Walker - Evasive Motorsports S2000 - 1:32.457
3rd - Robert Choo - DSport/Vortech/And1Performance S2000 - 1:33.739
4th - Charles Ng - Berk Technology S2000 - 1:33.850
5th - Jeff Tyler - Berk Technology BMW 135i - 1:34.241
6th - Manley Kao - TrackHQ/APR/Toyo Lotus Elise - 1:36.350
7th - Mike Bonanni - DoubleDownMotorsports.com 370Z - 1:37.286
8th - Rhys Millen - Hyundai/RedBull/Toyo/RMR Genesis Coupe - 1:37.392
9th - Kenny Chieu - Toyota MR2 - 1:37.385
10th - Jim Tway - Honda S2000 - 1:40.415
11th - Hiro Sumida - Toyota Cressida - 1:40.506
12th - Manuel Ortega - Bombsracing/Godspeed Project 240SX - 2:07.039

Here are some photos from the weekend courtesy of Berk Technology!

http://www.ddmtimeattack.com/rtawsir7.jpg

http://www.ddmtimeattack.com/rtawsir11.jpg

http://www.ddmtimeattack.com/rtawsir13.jpg

http://www.ddmtimeattack.com/rtawsir16.jpg

Here is a video as well. Sorry the position of the camera didn't capture much of any engine/exhaust sounds so I just put a song to it instead lol.

http://vimeo.com/4971642

Congrats, and great write-up! A few thoughts/questions

- Power steering... do you think changing to higher boiling point fluid would help at all? can you re-use your old mishimoto oil cooler core as a bigger power steering core? Also, I added +1.0 caster recently... I suspect with the added caster and reduced airflow from oil cooler placement, I'm going to start having the same issue... troubling, power steering pumps are not cheap
- Brakes... do you think it would be different if you had ample ventilation? we're going to try and get some ducting going in my car with same setup to try it out... I had serious brake fade as well last time out, but I'm going to work the air flow first before doing more upgrades/ swapping parts
- GTSPEC brace... did you ship mine yet ? :)
- LSD... I'll post thoughts on the carbonetic after this weekend, if we can get the car ready
- Fuel starvation! it is finally clicking... I had this issue a while back (first track day thread) and thought it was just limp mode, but it didn't feel the same... I now realize I must have had both limp mode AND fuel starvation impacting that day... happened on banked turn at PIR... there must be several ways we can fix this... prob deserves its own thread for discussion, if there is not one already

A better fluid might help, but I don't see it helping that much, especially if you go with a wider tire up front than stock. I don't think it needs anything the size of an oil cooler though. Despite the boiling fluid, the steering felt fine and there are no noises or anything coming from the pump.

Ample ventilation would help a bit but I don't think overheating is the cause of my issue. There wasn't any fade or soft pedal, just felt like the pad lost grip. It actually felt more like tire lock up, but I know it wasn't tire lock up since there was no smoke/noise/smell, and the car has ABS. Maybe even a vapor issue that can be solved with a slotted/drilled rotor.

lol, I haven't heard anything from GTSPEC that they are back in stock but I will check tomorrow.

Anxiously waiting!

I will let you do the honors of starting that thread sir. :D

Great post as usual Mike.

Regarding the fuel starvation, what about a surge tank?

Regarding the front camber issue, how could you tell, simply looking at tire wear?

Your car is rapidly becoming the benchmark for product evaluation, and your technically-inclined assessments help a lot, thank you!

If you stand on the brakes from a 140mph braking down to 40mph the surface of your brake pads could easily hit 1200 degrees, and then quickly drop. The HP+ pads just aren't cut out for that, you need a high temp track pad. Next time you take the wheels off you might want to check the pads and make sure there aren't any cracks from heat fatigue.

Great write up BTW, you would of seriously kicked arse in stock class.

Nice write up, great to get a feel for how the Z handles on the track before ever getting out there yourself. :driving:

BTW, wheels look hot :happydance:

Thanks! Yes a fuel surge tank would probably do the trick. As for the camber, I can tell by feel. The front tires would hop during long cornering which is usually an indication that they are rolling over onto the sidewall too much. They would also lose grip much faster than the rears which is another indication that there is too much heat in the part of the tire that is contacting the road. The true way to tell is by taking tire temps, but I didn't bother since I had no adjustment anyway.

Thanks to you as well! Track pads are definitely a must, but I have to say that I am impressed the HP+ pads took that much of a beating at Buttonwillow and around the rest of the track at Willow Springs before reaching the limit.

Thanks :)

Just watched the video as well. you can definitely tell this is a high-speed track. A lot of sweeping turns, so I can definitely tell how a little turbo MR2 was able to pull the fastest lap. A light car on a track with the ability to keep the car a full boost 95% of the time is a huge advantage.

Not to mention it was pushing about 450whp :driving:. Jeremy is a great driver too. Great driver + 450whp + Lightweight Mid-Engine platform = Win

well, that 450whp could have also contributed to it, lol.

Ok I uploaded the video to a different website now where the song works. Sorry, where I mounted the camera you couldn't hear the engine/exhaust so I just put a song to it. Still learning the GoPro Hero camera's sound limitations. At least I got video this time though. I mounted the camera on the inside hatch glass at Round #1 of the RTA series and the exposure was off so you couldn't see anything out of the windshield/windows. This time the video is good, but the sound sucked. Next time I will get both :D.

DDMotorsports 370Z at Redline Time Attack Round #2 on Vimeo

Yep, they do well, just can't handle the extreme high speed braking. I've used them on track as well and they work fine on the smaller tracks even if you have lots of frequent braking as long as it isn't long braking.

Great write-up, but its depressing to see a larger cooler (power steering) is needed.

Excellent post. As I suspected, the HP+ weren't going to hold on the track. That "glazing" effect is the same thing that we have all been getting. I'm definitely not going anywhere near the track again without new pads, rotors and lines. Enough messing around, if it happens on the wrong corner it will be a real shitty way to loose $45k.

I have a couple of questions on how you feel, like, dislike of other stock parts:
~Seats
~Shifter (Not sure you have changed this yet)
~Pedals (Which Z model do you have?)
~Steering wheel

Seats - They are fairly good for stock seats but I do have to use my knees to brace myself in turns. If I were turning this into a dedicated track car I would definitely get racing seats though, but since it remains my daily driver I will probably keep the leather/power/heated seats for comfort :).

Shifter - Love it. I am not going to swap it out. I personally don't like short shifters, at least none of the ones I have tried. Sure they are shorter throws, but they are a little notchy and because the stock shifter is smooth, I can actually shift faster with it than a short shifter. Short shifters also tend to increase my chances of mis-shifting, but maybe thats just a problem I have. These same issues I personally have with short shifters are on any car I have driven with a short shifter too (350Z, G35, Mini, Mustang, etc.). I just prefer stock shifters.

Pedals - I have the sport model and I have no problems with the pedals. I have never had a foot slip off and the orientation of them is easy for me to heel-toe, although I usually use SRM on the track.

Steering Wheel - The only thing I would change about the steering wheel in a perfect world would be to have it stick out farther. Like most stock vehicles, when I position myself where I want in relation to the steering wheel, my legs are too close to the pedals. I would like to extend my legs a little more and have the steering wheel closer to me. Other than that, I have no complaints. Again if this weren't my daily driver I would probably switch to a short hub/quick release/deep dish wheel combo, but since its a street car the stock wheel and airbag will stay for safety....and my radio/bluetooth controls :D.

Whoever designed the wheel had long arms and short legs (it's like Alfa Romeo all over again). I have the same problem as you, either you arms are too far away or your legs are too close. For street driving you can live with your arms a back a little but on the track you need to be closer for more control.

Yeah the Z is better than some other cars though. The Evo IX is the worst I have seen so far in that regard. Mini Cooper is pretty bad too.

Boiling power steering fluid
 

I did a track event this past weekend and after a run, had the car cooling with the engine running and hood up. A guy walked past and said my power steering fluid was boiling. Looking at the reservoir, there was quite a bit of centrifugal turbulence but no bubbles. While he claimed it was boiling, my feeling is the fluid viscocity has dropped so that the circulation is much more apparent. Turning off the engine, the movement in the reservoir stops immediately. Also, starting the car when the engine is cold results in a much smaller amount of turbulence in the reservoir.

Thus, I'm not sure it's boiling...just lower viscocity leading to more noticeable circulation of fluid.

Hmmm, I will have to experiment with that. Thanks!

I'm tempted to just drop the end of a meat thermometer in the reservoir during one of these 'boiling' times. Does that reservoir pressurize, or can I pull the cap when it's running and hot?

Just swapped brake pads and tires back to the street setup.

The Hawk HP+ pads look fine after the weekend. Wear is still awesome, after three full days on the track I would say there is still 80-90% left. There are no apparent signs of overheating. Everything looks to be in good shape.

I durometer tested the NT05 tires when they were brand new, and again just now when I took them off the car after two hard days at the track. Seems as though on average, they got a tiny bit softer after some good heat cycling on the track! The left front remained the same before & after, but this is also the tire that gets the most abuse at Willow Springs so my guess is that the tires get a bit softer with a few heat cycles then start to get harder. This seems to be a very consistent tire though as after two hard days on a really hot track, they are still a bit softer than brand new! I will have to start over when I switch to 18s, but I plan on keeping the next set of tires for a lot longer and will monitor their status more in depth.

So, about those track wheels?? :happydance:

also, about how much wear did you put on those tires in 2 track days? compared to the stock bridgestones? I know it was a different track with different wear, but just a general comparison.

As soon as I clean them up they will be ready to go :D. I would say there is probably a good 80% tread left on the tires, maybe more.

Sounds good, just let me know what you want for them and if you are planning on keeping those tires on them or just doing wheels only. :tiphat:

What settings are you using for the coilovers?

I made a lot of adjustments throughout the weekend but I think I ended up at full stiff on compression in the rear, 2/3 stiff compression on the front, and around 2/3 rebound all around. Give or take a few clicks of adjustment. :)

The settings will depend on the track and conditions.

I think the BC setup probably needs stiffer springs in the rear, that's the way this car is designed. By default they give you 2K softer in the rear which is the opposite of the stock configuration, and the Nismo. You were probably cranking up the shock settings in the rear to try and compensate.

I disagree. I think the 2k split is perfect. I was cranking down the front to try and compensate for the understeer from not having enough front camber resulting in not enough contact patch and overheating the outside edge of the front tires.

If you had a stiffer rear that would have helped load the front :p

But a good corner exit is the most important part of a turn and I love how this car squats and hooks up once you hit the go pedal on the exit of the corner. :D

There is still MUCH more development needed on other parts of the car before I start fiddling with spring rates. Like I said, spring wise this car feels awesome.

http://www.ddmtimeattack.com/buttonwillow61.jpg

The stiffer you make the rear in comparison to the front, the easier the rear can snap over steer on you...not a good thing unless you are in a drift contest. You want the front as stiff as possible to get sharp turn in and the rear softer for compliance and grip pulling out of corners, like DDMotorsports said about coming out of corners.

ChrisSlicks, where did you find the 370Z spring rates info? The stock rates certainly don't feel like 7.5k/8k F/R at all.

The stiffer you make the front springs the more understeer on turn in you will get as there will be left weight transfer to the wheel with grip. I haven't had a major problem with snap oversteer, it's pretty progressive when on the throttle. I found the specs somewhere out there, I'll try and find it.

perhaps we're confusing lateral stiffness with spring rates here? let me test my thinking - i'm sure someone will correct me if they see it different... :) with 100% stiff front springs but plenty of lateral compliance, should get grip on outside tire on even pavement... assuming lateral stiffness difference front to rear is a non-factor, seems to me that spring rate differences front to rear are more apt to impact things like rates of weight transfer fore/aft and rebound and compression rates... slow weight transfer to front would contribute to understeer, and could result from having relatively less compliance in front due to stiffer spring rate - that part i agree with