RX7 FC Track Car Tips and Tricks
07-28-11, 12:15 PM
#26
Spinning Dorito
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A bit of advice for when you get your car out, as long as you are exceeding 100 mph, aero has an effect. Look at all those unlimited Solo 1 guys in the US. It just means that the slower you go, the larger the wing required to have an effect. As well the front splitter will have to extend out further, but if I recall correctly, a report from Simon McBeath in Racecar Engineering stated that splitter effect dropped off substantially after it reaches 3" from the forwardmost point of the front fascia. I am running an AWR GT3 1 piece nose that Al got with nhis car when he bought it. It isnt the best fitting thing in the world, but it really does the job. Its very light, about 5 lbs for the whole nose and spoiler and setup.
The rest of your suspension setup sounds very good and I do have experience with the old GAB,s and AGX's from my Suzuki days. The shocks should be capable of controlling those spring rates when you are close to the firmer settings. Honestly, the only thing I would try is removing the rear bar for a test to see if it allows you to reduce wheelspin and increase your acceleration out of some of your tighter corners. A good bushing kit would be good as well as it controls the arms better and minimizes deflection and that vague feeling.
As a side tip, I used to have the straight ahead position of my steering wheel change during and after the race. For the longest time I thought something was slipping in the suspension setup like a control arm or tie rod or camber plate. What I found, during an engine pull, was that the rack was slipping back and forth in the rubber mounts. I shimmed the bottom up with shim steel until it was solidly mounted and I have never had that issue again. I think this also shows effects of bumpsteer and the use of bionics in the drivers forearms.
Something cheap and easy to do to the car to make the steering more precise.
Eric
The rest of your suspension setup sounds very good and I do have experience with the old GAB,s and AGX's from my Suzuki days. The shocks should be capable of controlling those spring rates when you are close to the firmer settings. Honestly, the only thing I would try is removing the rear bar for a test to see if it allows you to reduce wheelspin and increase your acceleration out of some of your tighter corners. A good bushing kit would be good as well as it controls the arms better and minimizes deflection and that vague feeling.
As a side tip, I used to have the straight ahead position of my steering wheel change during and after the race. For the longest time I thought something was slipping in the suspension setup like a control arm or tie rod or camber plate. What I found, during an engine pull, was that the rack was slipping back and forth in the rubber mounts. I shimmed the bottom up with shim steel until it was solidly mounted and I have never had that issue again. I think this also shows effects of bumpsteer and the use of bionics in the drivers forearms.
Something cheap and easy to do to the car to make the steering more precise.
Eric
The car has mostly upgraded bushings in it, but some of them are probably getting tired all the same. Probably a project for this winter.
I've actually been wanting to try unhooking the rear bar just for a test, but I've never made it far enough down my testing list without something more important happening to get me started from the top again. (i.e. transmission failure, engine problems etc.) But, after you and Al both commenting on lack of rear bar (I've seen a lot of the ITS guys mention it as well) I'll make it a priority.
Now, for the Aero. I have no speedo in my car, but judging from my lap times (I reverse engineered it based on gearing and RPM once, but I can't remember now) and the speeds I've hit on the same parts of the track with my RX8, I probably close in on 180-200km/h for a few seconds at the fastest part of the track, and probably close in on the 100mph mark at one other point. So, knocking on the door of aero being useful. Would probably be a bit more useful if I could get over a few mental blocks and get my foot in it. The car is capable of running about 6 seconds per lap faster than I'm capable of pushing it. (Car has run 1.17s at AMP in it's past.)
So, sounds like Aero is going on the list for this winter.
Any more information on what you are running for a wing?
As for the splitter, the AWR stuff is nice, but may be a touch out of my budget. I may have to dig up some of the home-brew threads.
07-28-11, 11:03 PM
#29
lol anyone going to shannonville on this long weekend? i think theres an event on monday. i would LOVEEE to sit passenger in one of your cars just to see how a fc performs on the track. all this talking about setups is making me want to get my rx7!!!! as soon as i get the right deal and enough money, ill finally get to join you guys!
07-29-11, 07:54 AM
#31
Rotary Freak
Thread Starter
To eliminate it completely, you need to raise the height of the inner control arm mounts, which is darn near impossible with the way they mount. If you lower your FC you will always have some bumpsteer unless the complete front end is fabricated from tubes, lol. You should see what they did to my Cougar to eliminate bumpsteer. Whooooo baby, they spent a ton of money and time changing the car.
Eric
07-29-11, 08:20 AM
#32
Rotary Freak
Thread Starter
lol anyone going to shannonville on this long weekend? i think theres an event on monday. i would LOVEEE to sit passenger in one of your cars just to see how a fc performs on the track. all this talking about setups is making me want to get my rx7!!!! as soon as i get the right deal and enough money, ill finally get to join you guys!
Eric
07-29-11, 09:42 AM
#33
Displacement Replacement
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http://mazdatrix.com/SteeringAngle.htm
these are what i plan on using eventually for my bumpsteer i'll just deal with it for now, i notice its alot worse with my 16 on compared to my 17's ,I use to bomb around in 6 wheel tanks that were older than me and many other canadian military gems lol my ride quality standards are alot lower than the average person
, but i do need to raise my car a bit
these are what i plan on using eventually for my bumpsteer i'll just deal with it for now, i notice its alot worse with my 16 on compared to my 17's ,I use to bomb around in 6 wheel tanks that were older than me and many other canadian military gems lol my ride quality standards are alot lower than the average person
, but i do need to raise my car a bit
07-29-11, 09:51 AM
#34
Rotary Freak
Thread Starter
Eric
07-29-11, 02:11 PM
#35
Go Hard....or Go Home
lol anyone going to shannonville on this long weekend? i think theres an event on monday. i would LOVEEE to sit passenger in one of your cars just to see how a fc performs on the track. all this talking about setups is making me want to get my rx7!!!! as soon as i get the right deal and enough money, ill finally get to join you guys!
07-30-11, 07:54 AM
#38
Go Hard....or Go Home
I an I dont post a price because most people have to make the mistake of building one to realize what a good price is lol. Jason if I sold my 7 the next one would be North American powered and drivelined so I could afford parts lol.
07-30-11, 02:59 PM
#39
Al and I will be there on Monday to do some testing. You will be able to watch, but no ride alongs as I know I can't put a passenger seat in my car and I am pretty sure Al can't put one in his. Come on out anyways as you will get to see Al and I goof around some while I have some testing chores, then we can play some as well. Playing in the cars is the funnest part. Tire lock ups, smoke billowing, big slides and maybe some off roading, LOL.
Eric
Eric
01-23-14, 02:16 PM
#44
No reason to go with the soft OE ones, I re-bushed with Energy Suspension pieces a couple seasons back, I didn't find it really made the ride harsher, although in some fairness, I'm running coilovers that are much stiffer than stock, although short of true race-car firmness, so my ride was already a bit harsh.
01-24-14, 08:37 AM
#45
Rotary Freak
Thread Starter
Honestly, I really like the Energy Suspension pieces as the compliant bushings in FC's. If you go to solid bushings you can get binding and false stops when the bushings reach their limit of distortion. You either have to go from a relatively compliant bushing like the Energy Suspension type, all the way to rod ends to allow for the twisting. The Mazda FC rear suspension is a maze of different rotational arc's and all of them don't line up for smooth rotational over the travel of the bushing. They want to twist a bit. Mazda built this compliance in for the passive rear steer on the stock suspension.
You can replace them all with iron like firmer bushings, but you can end up with a darty unstable car under suspension loadings. Just go with the firmer street style kits unless you are going full race and re-engineer the car.
Eric
You can replace them all with iron like firmer bushings, but you can end up with a darty unstable car under suspension loadings. Just go with the firmer street style kits unless you are going full race and re-engineer the car.
Eric
01-24-14, 09:05 AM
#46
Thank you guys for the info! What methods do you use to counteract the fact that we're limited to our Macpherson style struts instead of the more modern double wishbone suspension? Would it be wise to run stiffer springs and lower ride height to help mitigate the camber changes or is that just something we have to live with in our chassis design?
01-24-14, 02:59 PM
#47
Lowering is good, but excessive lowering can hurt your handling a couple of ways - and I'm not a suspension engineer, so if I misstate anything, people can correct me (like that's ever a problem on web forums!). Because the lower control arm mounting points can't be moved, lowering the car tends to lower the roll centre faster than the centre of gravity is lowered, which increases the roll couple - the effective lever length created by the difference between CG height and RC height. Although lowering the centre of gravity is good, increasing the roll couple isn't, since it increases the leverage of the weight transfer in cornering, and makes the car less responsive to steering inputs - meaning harder to drive at the edge. As has been mentioned earlier, bumpsteer also tends to increase with lowering, although there are tie rod ends that can be bought to deal with that.
Here's a couple of discussions relating to the effect of over-lowering stock suspensions - it's not a just Mac strut issue, Mac struts just suffer for the fact they tend to have little-to-no negative camber gain in under compression (so at-the-wheel camber quickly becomes positive at the outside tire due to body roll). Stiffer springs resist roll and help to fight the geometry change that results from the body roll changing the tire's camber - as will a stiffer front bar in particular on these cars, which also helps fight the inside rear tire lift that tends to go with a front roll centre that drops faster than the rear roll centre, which leads to changing the stock roll axis (already biased in most cars towards understeer), and increases weight transfer under cornering to the front outside tire.
A couple good articles on suspension geometry, specifically changing roll centre:
It's all in the geometry - roll-centre
Pro-touring.com - Negative Rollcenter Height
Here's a couple of discussions relating to the effect of over-lowering stock suspensions - it's not a just Mac strut issue, Mac struts just suffer for the fact they tend to have little-to-no negative camber gain in under compression (so at-the-wheel camber quickly becomes positive at the outside tire due to body roll). Stiffer springs resist roll and help to fight the geometry change that results from the body roll changing the tire's camber - as will a stiffer front bar in particular on these cars, which also helps fight the inside rear tire lift that tends to go with a front roll centre that drops faster than the rear roll centre, which leads to changing the stock roll axis (already biased in most cars towards understeer), and increases weight transfer under cornering to the front outside tire.
A couple good articles on suspension geometry, specifically changing roll centre:
It's all in the geometry - roll-centre
Pro-touring.com - Negative Rollcenter Height
12-06-15, 10:47 AM
#48
F**K THE SYSTEM!!
23Racer.
I recently collected some swaybars myself. Got the smallest OEM rear swaybar since everyone seems to remove theirs, so i figured it wouldnt hurt to grab it, just in case. I also finally added the adjustable front Suspension Techniques sway bar to my collection but haven't had a chance to use it.
My question is , are you use the OEM front swaybar on slower/shorter/tighter tracks?
I recently collected some swaybars myself. Got the smallest OEM rear swaybar since everyone seems to remove theirs, so i figured it wouldnt hurt to grab it, just in case. I also finally added the adjustable front Suspension Techniques sway bar to my collection but haven't had a chance to use it.
My question is , are you use the OEM front swaybar on slower/shorter/tighter tracks?
12-08-15, 10:00 AM
#49
Rotary Freak
Thread Starter
I just realized that I haven't added anything to this in years...
Lets see what I can add to this that can help and blow peoples minds. Also, its important to realize that Anduro's car is stupid fast and he has gone totally crazy by basically building a tube frame car inside the stockish shell. I think of it like building a ship in a bottle. His car is about the ultimate fabbed RX7 around here. The other thing is that my RX7 is a race car and not a time attack car. To an average outsider, they look sorta the same, but mine was built to handle racing speeds for hours and Andrew's is designed to go freakin' monster fast for 15 minutes at a time. Big difference.
Anyways, new learnings from the start of this thread. First and incredibly obvious, tires make a huge difference to how you set up and use your car. Last year, we were fortunate to receive new set of ToyoR888's and a set of Toyo RR's. Both are considered to be state of the art R Compound Streetish tires. Both sets in the same size of 225x45x15. They were as different as chalk and cheese. We put the RR's on for the 2014 3 Hour Indian Summer Enduro and with 2 new drivers, the car ran consistent quick laps in the 1:40.xx range and there was no drop off in performance no matter how hard they were abused on track. The car finished the race and the tires looked like new. They are an awesome tire, durable and fast. These are my new go to R Compound tire. We ran our standard Mosport setup of Stock rear bar set up full soft, Suspension Techniques front bar full firm, 650 lb front springs, 400 lb rear springs 0/0 front and rear toe and 4 degrees front camber and 2 degrees rear. The car ran well and won its class! Excellent day.
Now lets talk about the Toyo R888's. I expect that the guys at Toyo know their stuff, but good lord they are an odd tire to try to get your head around. Super greasy, over heats way to easily, you have to minimize steering inputs and they are slower than the 10 year old Toyo RA1's I have. No bueno. Save your money for the RR's. I expect someone in North America has made them work for them, but I don't even want to try. They have a great tread design, so I am keeping them for rains.
Lets talk about 2015 and the complete change in the RX7 from before. God, have I mentioned how much I love this car? It is like a bull terrier and goes through design changes and different drivers and just keeps on motoring and getting faster. In 2015, we were fortunate to receive support from the good people at NA Carrera Tires. These are a purpose built slick and a bias ply tire. These would require big changes to the car to make them work and man do they ever work! First a little design knowledge between a radial and bias ply tire. The terms refer to the way the internal belts are constructed and how they lay over one another. A radial has 1 to 2 belt layers where the belts are laid at 90 degrees to the direction of rotation. They then have a few layers of belts that are run at a bias of 45 degrees. These 2 90 degree belt layers supposedly allow the tread to shift laterally under load and keep the contact surface flat to the direction of travel. This is great as long as you don't slide the car and it is at these limits and feeling for the limits, where the average driver feels the car is nervous or a bit vague feeling. If you are skilled enough to keep the car just inside the slide point, they provide strong grip and wear well. The Bias ply tire lays all the belts at a bias across the carcass. What does this mean to the driver? In this case under straight for and aft loads, the tire is more compliant to the road surface and the contact patch goes up a bit. In the corners, the inside edge will progressively lift as the loads increase. This gives the driver a huge window of "Feel" and 90% of racers will go faster. The other cool things is that the cambers go back to as close to 0 as you can get them. Caster goes to stock, toe goes to stock. Basically these work great on dual duty cars and extend the lifespan of suspension parts as they are not being forced to operate at extreme angles.
So, with this in mind we returned every suspension adjustment on the pig back to stock. Left the springs and bars where they were, swapped on a set of the slicks and went out and raced it in the 2015 3 Hour without any testing and with 2 drivers who had really never driven the car at Mosport before. Oh yeah, to add another little wrinkle, it was damp and spitting for most of the race. We were in second place overall for most of the first half of the race and ended up winning the GT class. Takeaway, these tires are awesome. They transformed the car and it should be monster fast in 2016 and I can hardly wait to race it again. I am hoping to pull a 1:36 out of it.
Anyways, back to the thing that is going to blow your mind. In the whole time I have raced this car, at TMP, at Shannonville, at CTMP GP Track and at the Toronto Indy, I have always used the stock 4 bolt single piston front and unvented rear brakes. I have always played with the pads a ton, added a lot of functional ducting, changed the brake fluids often and yes even once melted the front seals out of the calipers, but this car works so well with these brakes that I am loath to upgrade them. My basic philosophy is that if the brakes can slow you down as fast as you want to, don't fade or fail, still lock up if you push too hard and are durable, then why change? They are the lightest setup you can run on the car. They reduce unsprung weight which is crucial to keeping the tires on the ground and they are cheap. Only issue right now is getting good race pads for the fronts. At the present time I am using a carbon ceramic pad made by a company in Ohio, KFP and its awesome. Durable, heat resistant and doesn't seem to hurt the rotors.
There you go, the latest and far overdue technical update on the pig. Still out there racing, still belching flame and still winning races for 17 years.
Eric
Lets see what I can add to this that can help and blow peoples minds. Also, its important to realize that Anduro's car is stupid fast and he has gone totally crazy by basically building a tube frame car inside the stockish shell. I think of it like building a ship in a bottle. His car is about the ultimate fabbed RX7 around here. The other thing is that my RX7 is a race car and not a time attack car. To an average outsider, they look sorta the same, but mine was built to handle racing speeds for hours and Andrew's is designed to go freakin' monster fast for 15 minutes at a time. Big difference.
Anyways, new learnings from the start of this thread. First and incredibly obvious, tires make a huge difference to how you set up and use your car. Last year, we were fortunate to receive new set of ToyoR888's and a set of Toyo RR's. Both are considered to be state of the art R Compound Streetish tires. Both sets in the same size of 225x45x15. They were as different as chalk and cheese. We put the RR's on for the 2014 3 Hour Indian Summer Enduro and with 2 new drivers, the car ran consistent quick laps in the 1:40.xx range and there was no drop off in performance no matter how hard they were abused on track. The car finished the race and the tires looked like new. They are an awesome tire, durable and fast. These are my new go to R Compound tire. We ran our standard Mosport setup of Stock rear bar set up full soft, Suspension Techniques front bar full firm, 650 lb front springs, 400 lb rear springs 0/0 front and rear toe and 4 degrees front camber and 2 degrees rear. The car ran well and won its class! Excellent day.
Now lets talk about the Toyo R888's. I expect that the guys at Toyo know their stuff, but good lord they are an odd tire to try to get your head around. Super greasy, over heats way to easily, you have to minimize steering inputs and they are slower than the 10 year old Toyo RA1's I have. No bueno. Save your money for the RR's. I expect someone in North America has made them work for them, but I don't even want to try. They have a great tread design, so I am keeping them for rains.
Lets talk about 2015 and the complete change in the RX7 from before. God, have I mentioned how much I love this car? It is like a bull terrier and goes through design changes and different drivers and just keeps on motoring and getting faster. In 2015, we were fortunate to receive support from the good people at NA Carrera Tires. These are a purpose built slick and a bias ply tire. These would require big changes to the car to make them work and man do they ever work! First a little design knowledge between a radial and bias ply tire. The terms refer to the way the internal belts are constructed and how they lay over one another. A radial has 1 to 2 belt layers where the belts are laid at 90 degrees to the direction of rotation. They then have a few layers of belts that are run at a bias of 45 degrees. These 2 90 degree belt layers supposedly allow the tread to shift laterally under load and keep the contact surface flat to the direction of travel. This is great as long as you don't slide the car and it is at these limits and feeling for the limits, where the average driver feels the car is nervous or a bit vague feeling. If you are skilled enough to keep the car just inside the slide point, they provide strong grip and wear well. The Bias ply tire lays all the belts at a bias across the carcass. What does this mean to the driver? In this case under straight for and aft loads, the tire is more compliant to the road surface and the contact patch goes up a bit. In the corners, the inside edge will progressively lift as the loads increase. This gives the driver a huge window of "Feel" and 90% of racers will go faster. The other cool things is that the cambers go back to as close to 0 as you can get them. Caster goes to stock, toe goes to stock. Basically these work great on dual duty cars and extend the lifespan of suspension parts as they are not being forced to operate at extreme angles.
So, with this in mind we returned every suspension adjustment on the pig back to stock. Left the springs and bars where they were, swapped on a set of the slicks and went out and raced it in the 2015 3 Hour without any testing and with 2 drivers who had really never driven the car at Mosport before. Oh yeah, to add another little wrinkle, it was damp and spitting for most of the race. We were in second place overall for most of the first half of the race and ended up winning the GT class. Takeaway, these tires are awesome. They transformed the car and it should be monster fast in 2016 and I can hardly wait to race it again. I am hoping to pull a 1:36 out of it.
Anyways, back to the thing that is going to blow your mind. In the whole time I have raced this car, at TMP, at Shannonville, at CTMP GP Track and at the Toronto Indy, I have always used the stock 4 bolt single piston front and unvented rear brakes. I have always played with the pads a ton, added a lot of functional ducting, changed the brake fluids often and yes even once melted the front seals out of the calipers, but this car works so well with these brakes that I am loath to upgrade them. My basic philosophy is that if the brakes can slow you down as fast as you want to, don't fade or fail, still lock up if you push too hard and are durable, then why change? They are the lightest setup you can run on the car. They reduce unsprung weight which is crucial to keeping the tires on the ground and they are cheap. Only issue right now is getting good race pads for the fronts. At the present time I am using a carbon ceramic pad made by a company in Ohio, KFP and its awesome. Durable, heat resistant and doesn't seem to hurt the rotors.
There you go, the latest and far overdue technical update on the pig. Still out there racing, still belching flame and still winning races for 17 years.
Eric
12-08-15, 10:17 AM
#50
Rotary Freak
Thread Starter
23Racer.
I recently collected some swaybars myself. Got the smallest OEM rear swaybar since everyone seems to remove theirs, so i figured it wouldnt hurt to grab it, just in case. I also finally added the adjustable front Suspension Techniques sway bar to my collection but haven't had a chance to use it.
My question is , are you use the OEM front swaybar on slower/shorter/tighter tracks?
I recently collected some swaybars myself. Got the smallest OEM rear swaybar since everyone seems to remove theirs, so i figured it wouldnt hurt to grab it, just in case. I also finally added the adjustable front Suspension Techniques sway bar to my collection but haven't had a chance to use it.
My question is , are you use the OEM front swaybar on slower/shorter/tighter tracks?
Eric
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