Car preparation for the 1/4 mile

[Glenn Butcher]

Bish - great idea with this thread. Maybe we can put something together out of this thread and mate it a Sticky for Car Preparation on the strip etc. We will do a seperate one for the circuit, as I personally think that circuit racing is harder on the whole car in general.

I'll try and help out here if I can.

I can only really go on what I have done myself, and what I have seen at the Drag track for car preparation (been a while since I have run a car properly on the 1/4!).


As the hp starts to increase, all sorts of problems in the driveline start to occur. But also at the engine itself. I'll start at the engine and work my way back.

ENGINE:

Tuning has to be the number one thing, but also all the things like regular maintenance are important. As many of you guys drive your cars on a daily basis, a lot of the small things are sometimes forgotten before going to the track.

* Make sure your oil/oil filter is changed regularly.
* Oil level is ok (3/4's to full is perfect) - no less no more
* Make sure your plugs are reasonably new
* Check coolant levels
* General visual check over the engine bay
* Others...

Probably goes without saying, but have any of those small problems corrected that have been bugging you like oil leaks etc.. If you think something isn't right like strange noises from the engine, missing in top revs, slight hesitations etc. - then forget it, something is bound to go wrong.

As for keeping temperatures down, when you are in the staging lanes - push the car whenever possible, it all helps. Moving on from this decent front noses, bonnets, intercoolers, cold air intakes start to become essential.

Tuning is important, and extra important with a rotary engine - as even one detonation can kill an apex seal. All those things that have been said over the years still apply here. e.g. If you have a standard FD but a large exhaust on it - then you may get boost spikes/creep etc.. So have it checked with a proper boost gauge, and wide-band lambda sensor for rich/lean indication preferably on a rolling road.

All the other things like a good fuel system need to be in place, if you think your injectors aren't flowing what they should be (i.e. hesitation at various revs etc. then don't bother racing it - have it checked, it may just be that the injectors need to be pulled out, cleaned and flow tested). Use things like a Fuel Pressure gauge to check pressure is a good idea (even a temporary one).

I'm sure there is a load of other stuff - please feel free to add (I got some other stuff to do now...).


CLUTCH/GEARBOX/TAILSHAFT/DIFF:

Some of the guys with big hp are now finding problems in this area - this becomes even more apparent at a properly prepared drag track. FD drivelines are reasonably strong, but were not designed for 400+hp and sticky tyres with 6000+rpm launches. Back 10-12 years ago we found this out with the older Mazda's here in Oz, in the time I owned my RX-2 I would have changed the diff. around 5 times, and went through countless numbers of axels. It was inevitable that Ford 9inches needed to be installed etc. - almost every quick Rotary Powered car in Oz now has some kind of extra strong aftermarket differential. Many people are also running auto's now, or again stronger gearboxes.

Sorry - have to fly, will post again later.

[Glenn Butcher]

Perhaps some of your seasoned 1/4mile racers, Carl, Ross, Geff, Tim, Clive, etc. etc. can post up some of your own personal experiences here to help out.

[BUZNUTS]

Give us a case to study and we can try to give you a list of mods and their effects on the 1/4
REgards-Anthony

[Glenn Butcher]

Jump on this opportunity guys, there aren't many people in the world that can tune a 6 second rotary, Anthony knows his stuff.

[bnaellis]

Hi Anthony,

Here's good example for a case study. I have 368 rwhp 337 ft lbs rw torque on a 94 rx7 hks to4r turbo 0.84 a/r housing etc etc
I have hks adjustable coilovers but the rest of the suspension is standard bushes trailing arms etc, along with standard diff 4.1 final drive and standard gearbox. Car has been given lots of hard driving including launches on the street. But the first time I took it too 1/4 mile track I lower my tyre pressure (standrad jap street tyres) to 27 psi I did a burnout for about 5 secs nothing excessive creeped forward till stage lights were lit reving to about 4,00 rpm lights go green I lift off clutch and hear a clattering noise and i'm not moving. Officials run over and point underneath my car lots of oil and metal. I had a broken diff casing was cracked and main shaft was in half.

1 week later I have a replacement diff although the only one available was from a auto 3.9 final drive gear driving on the street giving minimal abuse and it all seems fine. Go to the 1/4 track again last weekend have in my memory what happened lastime so no burnout at all this time. take off from the line at 2,500 rpm I bog down due to lack of revs. The revs then build up I think around 5,000 rpm I get some wheelspin and hear clattering and no more acceleration. This time I find that I have broken my diff again out casing as last time cracked in two all the way around internal gear is sitting on the floor, damaged a driveshaft the end of the splines were rounded and the piece where the cv gaiter is (closest to the diff is sepreated from rest of the drive shaft, also my gearbox has gone very noisy in all gears and neutral and no 3rd gear. All of that from a very gentle launch.
Other guy's running similar or more rwhp & torque with standard diff giving lots of abuse but no problem unlike me :confused:


rgds

[scooby_si]

Another thing i understand the importance of not overheating for intake temps etc & leaving engine off but say at an event like rotorstock where you may of turned up & car had totally cooled down overnight etc before you took it for a run i presume you'd need to warm it up again before giving it a portion of both turbos? Only i know the risks of overheating & it is good to avoid it i guess but i rarely see it mentioned so much about warming up fully before giving it death <a href='http://www.smileycentral.com/?partner=ZSzeb008' target='_blank'><img src='http://smileys.smileycentral.com/cat/15_1_60.gif' border=0></a> either.....
So what is best heat range to be in etc for the 1/4 in a rotary/RX7 engine/oil well warm but get intercooler as cold as poss with water or wotever?
Cheers
Si

[MikeLMR]

What about tyre pressures ? I know its a big advantage to drop the pressure in the driven wheels and raise the pressure in the non driven ones, but how much pressure to use (I know its going to be dependant on the tyres but a rule of thumb would be good)

[Archbish]

drop the rear ones 4 thumbs, and raise the front ones 2 thumbs.








what?

[bobster]

I personally would do my first few runs at the street pressure. And see how the car is liking or disliking the traction it gets. Then just experiment with different pressures. The fronts can stay as they are. I ran my rears at 20psi but it is just a personal choice thing.
It is just down to the tyres and how hard you are prepared to launch it.

[BUZNUTS]

350+RWHP from a .84 Exhaust housing (assuming P trim wheel) is going to give you one of the biggest torque figures at arund 5.5Krpm, so if you will break anything it would have been right there. Not sure if the second break was indirectly caused by damage from the first failure but could be possible. I have set up some mid 10 sec FD's with fundamentally std rear ends, so I am assuming another fault in the rear end. I would look at the torque location bar that joins the diff to the gear box and the condition of the heims in the tracking arms to the rear axle. Loose bushing in the rear enables the rear end to wind up and create more of an impact shock on all of the components(aswell as axle tramp). I have mounted the actual diff centre as well as the rear engine mounts on solid alluminium bushes also.
Try to adjust your suspension to as soft as possible bump(compression) and 3/4 hard on the rebound to try to promote maximum weight transfer. Be cautious when promoting weight transfer as the ammount of squat you achieve will directly affect your rear camber or tyre footprint, Not having your front suspension too low or limited in its travel also encourages good weight transfer.
While all of the above is an attempt to improve the et of your car, the most common reason for your type of case is a far too severe clutch (diaphram pressure that strikes the tyres way to hard and smashes rear end components. Other possible effects can be caused by excessive side wall strengths that transmit this shock back to the rear end without any cushioning of a soft wall drag style tyre.
Perhaps you could pick an issue you feel may apply to your car and we can go through it issue by issue.
REgards-Anthony

[Archbish]

Yeah, that's what I was thinking too.

[bnaellis]

Thanks Anthony,

The hks suspension is quite soft setup for drag racing launching on the road it does not spin the wheels just really good launches.
Ride hight is normal at the front and a little lower at the rear.
I will check the bushes in the rear suspension. The power plant frame between the gearbox and diff is not bent or anything. However the hks clutch and lightened flyheel extremely harsh so suspect this maybe a big factor. My torque is not anything to brag about at the rear wheels but it is quite broad I will post my dyno sheet it may assist. Thanks for your help.
Actually on one of the upper arms I remember someone advising me when I was changing the diff that one of the bushes was worn at the rear.

rgds

[bnaellis]

dyno sheet.

[maximtaylor]

Is there any way to lessen the 'shock' to the transmission by good launch technique Buznuts????

I have heard of using the handbrake to load up the transmission on the line?

Max

[cjle17]

Even on a slightly hopped up R1 the transmission takes a hell of a beating. First time out at the Pod ran 6 times and I snapped the power plant frame and disintegrated the clutch, it ended up blowing up and enbedding bits of clutch disc into the flywheel - doh!

So 1 and a half minutes of racing cost me £700 in parts and labour. Was it worth it - hell yeah. I smoked a very hopped up Skyline amongst other things even with aknackered clutch!!

[antnicuk]

Buzznuts, or Glen,
I have an Fd which consistently runs 12.5 on cheap street tyres. The car is in stock trim inside, and i dont want to ruin a really nice car to get the times down. But i want to get a quick car on the strip so i have recalled my old Gen 1 mk3, it was an elford turbo but now has a TII gearbox, and a 1988 13b turbo engine, (the predecessor for the TII). The steering is an egi rack and pinion but apart from that it is stock suspension and brakes. I am going to strip it down a little to shed some weight but i want to keep it road legal.

What can you recomend in relation to the rear end and also the engine. I'm not sure whether to port the FC engine or to try an RE or REW engine, as it has much bigger inlet system. I have a Mits TD08 turbo 22b which i want to fit. (i believe its similar to a GReddy T88), I dont care what it drives like on the road as long as i can drive it to the strip.

Any advice would be helpfull. I would like to get in the tens but dont really want tub out the rear end. Obviously slicks will be fitted at the strip.
Regards
tony

[Glenn Butcher]

Hi Tony!

Anthony hasn't been around for a little while - I'll have a go.

Going the 1st gen. is a great idea, it is much lighter than the FD - and you will be able to run pretty good times with it (along with your engine combination).

In standard form, it should be able to get into the 12's without too much hassle (and around 1BAR of boost).

As for the rear end - it is quite a dilemma, I personally would spend a little bit more and have a 9 inch installed. You have a great choice of ratios and it will be very difficult to break/axels are also strong etc..

Some guys out here run the Mitsubishi Hilux Diff's with pretty good success - but the ratios are limited.

The gearbox you are running will be quite strong, if it is in good condition you should be able to run some pretty good numbers.

As for the engine, I would stick with what you have got for now - is it running Microtech? You can still run into problems like boost spike/creep pretty quickly if you are running a straight through exhaust (I use to run a 3inch on my Series 4 turbo engine, and had leaning out issues!).

You will probably need to run a larger injectors/bigger fuel pump (I'm assuming it would have an aftermarket fuel pump in it of some sort?) - put a fuel pressure gauge on it also.

Also get a good tune into it.

Companies like www.pacperformance.com.au sell Fuel systems, which would be perfect for what you are doing. Link here: http://www.pacperformance.com.au/content/lang__en/tabID__3931/Parts/Fuel_Systems.aspx (makes it very cheap for you in £'s).

Clutch maybe an issue also.

Get onto www.ausrotary.com and have a look to see what some of those guys have set-up (there are a number of Series I, II, III RX-7's with 13B turbo's).

I actually can't believe that there aren't more 1st gen's running on the strip there, compared to an FD they are a very cheap car to get running some serious numbers.

[antnicuk]

Hi glen, thanks for the info,
I will do the same mods on it that i have done to my FD as they are proven, ie, ported, (i may try to bridge if i can some templates), two fuel pumps, two regs, 850 prims and 1500 secns, I just want to make sure that doing all the mods on the FC engine will not be ultimately restricted by the small throttle body and inlet runners. I dont think i can fit RE inlet manifolds on the FC engine. The REW enigne are quite a bit bigger and the RE bigger still. If i keep the FC i will go micro tech unless i can get the FD sensors and TPS to fit and then i will go Apexi PFC as there are more people to tune it and i would like to learn to do it myself.
Do you have to make a hole in the floor pan to fit the 9" diff or will it fit underneath? I want to have to tub the rear end out as elfords are quite rare and i dont want to make ireversable mods.
regards
tony