GSR Autosport Global Time Attack M4

[consolidated]

Originally Posted by Merli

I wouldn't say "incorrectly"...

There are a lot of terrible drivers out on the road who can afford performance cars who love to jerk the wheel into a corner while still standing hard on the brakes, or unintentional trail-braking through incompetence which could lead to disasterous results on the street if cars were delievered with more neutral brake bias.

Big front brake bias, and understeer-biased setups are right for 98% of the driving population IMHO.

If someone has the driver training, experience and skills to intentionally alter the brake bias (and suspension characteristics) to suit their driving style, then excellent! ... But I'm happy with manufacturers setting up cars to cater for the lowest common denominator, so some idiot next to me doesn't spin the car across 4 lanes and take out a bunch of cars while doing so.

We're talking track and race cars with race drivers and car control skills. Since you missed my point, why would you add MORE front bias with after market pads even for the everyday driver? It's already built in.

[Merli]

You're right... I did miss your point and read the following sentence in isolation and completely out of context

Most street cars can use more rear pad as manufacturers don't want us spinning off tail first under any circumstance, common logic is to just incorrectly put more and more friction in front.

My bad... Carry on!

[Diver]

Time attack, is that like a Tardis? Awesome!

[consolidated]

Originally Posted by Merli

You're right... I did miss your point and read the following sentence in isolation and completely out of context



My bad... Carry on!

[greekcs]

Cant wait to see it at SEMA.

[FTS]

Originally Posted by GSR Autosport

It's a good question. We have a big issue with that on the newer 911s we run/support at the track. If the ECU sees too big a difference it goes into ice mode which is no bueno on the track.

997.2 and 991s ABS is programmed to compensate for no more than 0.3" rolling diameter difference between front and rear, rear being higher. Any more than that the ABS and PSM get 'confused' and make the wrong evaluation of a given situation. I wish Ice Pedal was the only issue, but it is not. This is valid with both Bosch and Siemens units btw.

[surewin]

Nice lap on Buttonwillow!

[GSR Technik]

Originally Posted by Diver

Time attack, is that like a Tardis? Awesome!

A Mark 40 TARDIS... the original waaas blue... maybe this is the modern day Time and Relative Dimension in Space machine. With better aero of course.

[Savory]

Is the bumpiness from soft spring rates? Lower roll center?

[Black Gold]

Originally Posted by Savory

Is the bumpiness from soft spring rates? Lower roll center?

its almost always due to two things

1) inappropriate spring length for the damper length. the damper only has a certain amount of travel built in, and is specifically designed for a certain spring height. when you lower a car, the damper is already pre-compressed at static height, eliminating however much travel you drop the car by. you drop it an inch, at static height you already pre-compressed the damper by and inch and removed an inch of potential travel down before hitting the bump stops. so, you have made it more likely you will hit the bump stops, have made the dampers work in an inefficient range, and eliminated the majority of the travel. this is a HUGE issue and is why proper coilovers have shortened dampers to account for running a shorter spring.

2) wrong spring rates for the OEM dampers. the OEM dampers are designed for the exact spring rates in the OEM car. this is why a ZCP suspension will come with different springs (shorter) AND different dampers. because the length of the damper will be shorter and the compression rates will change due to a changing spring rate with the ZCP springs.

Overall, these springs cause a huge amount of issues which are exaggerated when driving on non ideal roads which have the dampers working hard. any "benefits" of these spring kits are vastly overshadowed by the negative effects. Not to mention the fact that most of these springs run progressive rates that are completely undisclosed, so no one has idea how any of these spring rates match to the stock dampers.

I don't blame the OP for testing them, I think its a good thing. Its a difficult thing for a performance shop to discuss a product they sell in a negative sense. I give them credit for being relatively honest about the springs and how they drive.

[swifty]

Thanks for the feedback. Been learning a lot from reading this thread. Some info was shared in previous threads similar to this but I think this is one of the rare ones where track data was shared by someone very knowledgeable in the technical aspect as well as the driving. Wish OP would try out the M specific springs for these cars to see how they stack up.

Originally Posted by KennyPowers

"this is why a ZCP suspension will come with different springs (shorter) AND different dampers. because the length of the damper will be shorter and the compression rates will change due to a changing spring rate with the ZCP springs."

Kenny, just wanted you to clarify one thing. Are you stating that the ZCP dampers will be shorter as well? If so, was that true for the e92 zcp?

[jackkk]

Originally Posted by GSR Autosport

Having more seat time now in the M4 I think the answer is somewhat yes and no. If you really want to put down some good times you really need to move to a performance oriented damper.

We tried the lowering springs mainly because we were looking to get more front negative camber (we were able to get -1.8), which is not ideal but something... again trying to deal with the understeer issues. With a lower CG the weight transfer of the car was a bit better but because of the reduced operating range of the damper and the fact that the H&R 435 springs we were using were not heavy enough to support the compression weight under load, high speed cornering composure was less than ideal.

Willow Springs was not a good track for the lowering springs because it is a fast, flowing track with bumps in critical braking areas (Turn 1) and corners (Turn 8). There aren't too many technical sections where you need to aggressively transition the car. I would expect the stock spring setup might be better at this track.

Now Buttonwillow is a much more technical track so transitioning the weight of the car is much more critical. It's also very smooth as it was just recently paved. I think the lowering springs could actually help at this type of track.

If you are just doing a track days for fun, every once in awhile I think the lowering springs are fine just note there limitations and be cognizant of the potential behavior changes in the car when you load up the suspension.

-Nick

Tnx a lot! I didn't see the first video, so I decided that it was the same track.

I'm thinking in getting the HAS KW kit. An if the camber plates will be available for the stock adaptive dempers it will be cool to make changes before the tack day and then go back for the street set up. Plus I drive the car at winter and I need the winter high set up. This is the reason I don't want to go with the coil overs, that I do around 3 track days a year because of the weather and free time.

So you posted before about the flash on this car. Will it be or not? I'd like to have a good linear flash for the car. I don't really like the piggy backs that give power only at mid range and make car uncontrolable at the track when you open the corner. Plus I don't want to loose the power till the top end (7600rpm) like in stock.

Tnx.

[GSR Technik]

Originally Posted by Savory

Is the bumpiness from soft spring rates? Lower roll center?

First, we are really using these springs for an unintended use. These are street lowering springs for a 435 that comes with 225/45-18 street tires with a pretty high tread wear rating. The spring rate was probably determined based on vehicle dynamics expected in a street environment. For their intended use (on the street and lowering your car) they absolutely fit the bill.

Now, when we take them to the track, put big sticky tires on and generate well over 1g in cornering forces things begin to break down but we shouldn’t be surprised.

It’s important to remember that springs generate force over distance and dampers generate force with speed. Springs need to support the forces (i.e. weight), ideally within the operating range of the damper. Dampers need to control the frequency of the springs.

In this case we are generating too much “weight” for the spring – fundamentally this is the biggest issue using these springs on track with an aggressive tire setup. The spring rate is not enough and compresses on to the bump stops.

We are reducing the operating range of the damper with a shorter spring but I don’t know enough about the construction of the damper internals to know if we increased the spring rate the dampers could handle the springs within that reduced operating range. I expect not but I don’t have any objective data to comment with any measure of confidence.

[GSR Technik]

Originally Posted by jackkk

So you posted before about the flash on this car. Will it be or not? I'd like to have a good linear flash for the car. I don't really like the piggy backs that give power only at mid range and make car uncontrolable at the track when you open the corner. Plus I don't want to loose the power till the top end (7600rpm) like in stock.

We had a deal with a company in Europe to provide a toolkit to be able to flash tune the S55 motors. Once we got close to finalizing the deal they wanted more money, a lot more money, to deliver what they originally agreed to. Unfortunately we had to bow out because we just didn't have the money they were demanding. Like most, we are now searching for a solution. The only guys I know who are able to tune are those with the OEM developer toolkit which are few and the car must be present.

[GSR Technik]

Originally Posted by swifty

Wish OP would try out the M specific springs for these cars to see how they stack up.

swifty,

We ran the stock springs at the first test day at Buttonwillow with R888 tires (100 tread wear), supposedly stickier than the tires we ran at the Willow Springs test - Hankook RS-3 (140 tread wear).

The challenge from the first test is we had so much understeer in the car we probably weren't generating as much cornering forces as we were during the second test. During the first test at Buttonwillow there is a long right-hand corner (Riverside) that is comparable to Turn 8 (where we think we were bottoming out the dampers) at Willow Springs, although it is a little slower (90 mph compared to 125 mph) and a little less bumpy. I didn't feel that the dampers were bottoming out in the Riverside Corner with the stock springs. When a get back to the shop I will look at the data from the two corners and see if there was a big g load difference. Will post what I find this weekend.

[M4isKing]

are you guys by chance doing open testing tomorrow at buttonwillow?

Would love to check out the car in its natural habitat. Yes, get rid of those springs!

[GSR Technik]

Originally Posted by M4isKing

are you guys by chance doing open testing tomorrow at buttonwillow?

Would love to check out the car in its natural habitat. Yes, get rid of those springs!

Unfortunately no, car is being prepped for SEMA. We won't be able to test again until after SEMA.

[HP Autosport]

Originally Posted by KennyPowers

this should read "because lowering springs with stock dampers are terrible for performance"

So F8X and E9x alike, H&R may not have spent enough time in R&D and resulted in these issues. What is the hurry to come to market with a product that has not been thoroughly tested?

***Just read 435i springs were used....that is part of the problem***

[GSR Technik]

Originally Posted by HP Autosport

So F8X and E9x alike, H&R may not have spent enough time in R&D and resulted in these issues. What is the hurry to come to market with a product that has not been thoroughly tested?

I don't want to answer for KennyPowers but it's our opinion that they are fit for purpose - on a 435 for spirited street driving. No for track duty on an M3/M4.

[VMRWheels]

Beast, good stuff!! Looking forward to seeing more updates

[psuibmw]

Get rid of the wing ... Does not fit IMO

[GSR Technik]

Originally Posted by psuibmw

Get rid of the wing ... Does not fit IMO

Going for function over form since we are competing in time attack. Would never really run this on the street. We bought a whole extra decklid so we can swap back to stock decklid with M Performance spoiler easily.