Autocrossing with a Lightended Flywheel? Helps or hurts? (MK1 VW Rabbit)

Hi everyone,

So my clutch is starting to go out on my 84 VW Rabbit GTI and I need to replace it. It's a stock CIS 8v with a 4K trans for those familiar with the cars. I should also mention that it has a close ratio trans with 3.45/2.12/1.44/1.13/0.89 and a 3.94 final drive. It moves through the gears swiftly but revs up pretty high at highway speeds.

Clutch feel wise even before I could tell it was starting to slip recently, I've had trouble getting clean, consistent launches. Most of the time when driving around in town I actually start out in second because 1st often feels like a "granny gear" to me. Even starting from second I'm sure that I am losing time when autocrossing. Granted this is with a deteriorating clutch that may very well be the original on a 33 yr. old car and with shift linkage that needs a rebuild, both of which I plan to remedy.

This is not a daily driver, but it's also not a dedicated autocross car either. I'm not backing it off the trailer on slicks. I'm using it for normal street driving with the occassional long distance trip to car shows, etc. as well. Whatever I do I don't want to make it agrevating to drive on the street, or a serious pain in the ass if I'm stuck in stop and go traffic on the freeway in Chiago for example.

So with that being said, there are 2 options I'm seeing for clutches although I could do a combination of both if I wanted to.

1) A "Stage 1" clutch with a 16v vw pressure plate and stock 8v clutch, stock flywheel. The pressure plate is beefier and is said to stiffen up the clutch some and can handle more power.

2) A lightened flywheel setup (with or w/o 16v PP). The 2 I've found are either 7.75 lbs. or 8.9 lbs. vs. the stock 12.5 lb. flywheel.

From what I've read it will make the motor rev faster with less flywheel mass but may also chatter at idle, be harder to launch, and could make acceleration kind of jerky from the RPM drop if I let off the gas on the highway. I'm leaning against it.

However, the question I really want to ask here is:

Is a lightened flywheel is actually helpful for autocross?

If so why?

Is it worth the sacrifice of drivability?

Would you do it to a street car?

Contradiction wrote: Is a lightened flywheel is actually helpful for autocross?

Not sure. I would think so.

Contradiction wrote: If so why?

I've never autocrossed back to back with/without to see any time difference. Once the car is in motion though, I'd think the quicker rev matching if shifting would be of benefit. I'm sure other veterans will have better data.

Contradiction wrote: Is it worth the sacrifice of drivability?

Yes, IMO. I've never noticed any downside in driveability. I've had 3 different VW's as daily drivers with lightened flywheels. I prefer the quicker responsiveness and rev happy nature of the motor.

Contradiction wrote: Would you do it to a street car?

Yes. Every time.

Is it helpful? I can't seem to tell a difference with the 10lb flywheel in my Miata, honestly.

Is it worth the sacrifice? It didn't take much for me to adjust, just goose it a little more when starting, although other people have stalled it.

Would I do it in a street car? I already did.

My only experience with a lighter flywheel was my 99 Accord. Went from about 24lbs to about 12. Essentially to about what you have now.

No drivability issues, but I guess that 12 lbs. I that light.

I should throw in one more thing I forgot to mention, I am currently NOT Heel Toe Shifting and rev matching when I drive. I would like to learn at some point though.

xflowgolf wrote: Yes, IMO. I've never noticed any downside in driveability. I've had 3 different VW's as daily drivers with lightened flywheels. I prefer the quicker responsiveness and rev happy nature of the motor.

Thanks Nick. What have you ran a lightened flywheel on?

Your Crossflow ABA? Have you had it on any 8v's? Do you recall how light you went?

I'm looking at the USRT 8.9 lb. most likely. BFI makes a 7.9 lb. but it's more expensive.

Contradiction wrote:

xflowgolf wrote: Yes, IMO. I've never noticed any downside in driveability. I've had 3 different VW's as daily drivers with lightened flywheels. I prefer the quicker responsiveness and rev happy nature of the motor.

Thanks Nick. What have you ran a lightened flywheel on? Your Crossflow ABA? Have you had it on any 8v's? Do you recall how light you went? I'm looking at the USRT 8.9 lb. most likely. BFI makes a 7.9 lb. but it's more expensive.

It's been awhile. Yes 2.0 ABA 8V had ~9lb. flywheel i believe. 2.0 16V Scirocco ran lightened.

My 1.8T B5 Audi A4 had an aluminum Fidenza lightweight flywheel. That was the only one that chattered, but it was more the multi puck clutch (which I later swapped clutch, kept flywheel, and eliminated the chatter). Never had an 020 trans (Mk1, mk2, mk3) chatter.

A "stock" lighten flywheel should not be an issue on the street or track. A light weight aluminum flywheel would have some of the issues you mentioned. I have a 16V Scriocco and a lighten stock flywheel. My gear ratios are similar to yours other than final being 3.67:1. No clutch related issues at all.

Depends on your autocross classing too! Many classes do not allow a lightened flywheel.

Although ive only used aluminum/lightened fw in road racing it certainly seemed to help MUCH more accelerating and to a slightly lesser degree with compression braking. Absolutely no problems with chatter. Really woke the car up...much bether throttle respnse.

trucke wrote: Depends on your autocross classing too! Many classes do not allow a lightened flywheel.

Hadn't thought of that but good point! I'll have to see if it's allowed for STS.

In reply to Contradiction:

Another vote for the light flywheel if your classing allows it.

And I wouldn't spend extra $$ on a clutch that can handle more than stock power if you're keeping it at stock power.

I used to run an 8lb flywheel with 16V pp in my 8V hybrid and loved it. Yes, the starts are a little jerky without the extra mass to smooth it out. But making the 8V rev faster more than makes up for it on track.

I drove that thing on auto-x, track, and street.

In El Rabbito I run a Eurosport ~9lb flywheel with a Tectonics 4 puck unstrung race disc with 16v pressure plate. No issues with loss of torque etc. Great improvement to throttle response and rev happiness. I use mine for commutes on nice days, errands, as well as the Autox it's primarily built for.

The only change I'll make next time is a sprung clutch as the unsprung clutches are like a light switch with no launch under 2500 rpm doable smoothly.

In reply to Contradiction:

All ST classes in SCCA autocross require using a stock clutch, flywheel, and pressure plate. That means stock replacement type parts for all. Non-stock clutch parts will move you to FSP.

pretty sure changing the flywheel will move you out of STS, at least with scca rules. I just did the same upgrade. Now im no longer in sts. Not really a concern for me, but maybe for you.

Thanks for all of the feedback guys but it looks like I can't do the flywheel. :(

trucke wrote: Depends on your autocross classing too! Many classes do not allow a lightened flywheel.

I think truke is right based on what I just read in the rulebook. I’m afraid to think that the “No Fun Police” are going to strike me down again.

It says nothing about a lightened flywheel in the ST rulebook section so am I correct in assuming that if the rulebook doesn’t mention it means I can’t have it in that class? It doesn't mention the clutch or flywheel in that section at all for that matter.

I am wondering if an 8v clutch and 16v pressure plate may be permissible though? Technically the 16v PP is an OEM part and it’s an interchangeable component on most 020 transmissions from the MK1 – MK3.

So would the fact that it's an OEM for another model code of this trans make it okay?

Or would the arguement be that it only came on a 16v or ABA block and not a CIS 8v so it would be updating to a newer generation part?

Is autox really your main concern with this car? Ive taken the aproach of build what I want, and get classed where ever. Im out to have fun, classing really dosent bother me. Unless your specifically trying to build a national level sts car.

79rex wrote: Is autox really your main concern with this car? Ive taken the aproach of build what I want, and get classed where ever. Im out to have fun, classing really dosent bother me. Unless your specifically trying to build a national level sts car.

For now at least it is. I feel like I want to give it an honest go to stay in a particular class for at least the next 2 years until I feel like my skill level increases enough that I can make an honest assement of whether or not:

1) I am a half way decent driver and I should even worry about what class I'm in to compete regionally or nationally.

And

2) If my skill level is adequate is the car itself competative in my class?

Last year I did 4 or 5 events and I flat out sucked. This year I'm making strides and getting some compliments from other drivers who saw me run last year and I'm at least creeping up into "mid pack" for times. I'm still getting my ass whooped by 4.5 - 5 sec. in STS against more experienced drivers.

I hate to go up to FSP right now becuase I'm not going to run R Comps, get a LSD, do some port & polishing, etc. to really take advantage of the class allowances.

However, in a few years if I just don't feel like me or the car are truly competative then I'm going to build it the way I really want to and just run for fun and let it be a SM car for all I care.

Contradiction wrote:

79rex wrote: Is autox really your main concern with this car? Ive taken the aproach of build what I want, and get classed where ever. Im out to have fun, classing really dosent bother me. Unless your specifically trying to build a national level sts car.

For now at least it is. I feel like I want to give it an honest go to stay in a particular class for at least the next 2 years until I feel like my skill level increases enough that I can make an honest assement of whether or not: 1) I am a half way decent driver and I should even worry about what class I'm in to compete regionally or nationally. And 2) If my skill level is adequate is the car itself competative in my class?

I think question #2 is more important now. Is a mk1 GTI even reasonably competitive against other cars that class against it built in the last 35 years?

I really don't know the answer to this.

Different strokes for different folks, but it seems a bit silly to not mod a car for your own enjoyment the way you want to, if it's something that could never be competitive within it's class anyways.

Jason, My car had stock flywheel and clutch, I replaced the clutch (with stock) just before I sold it to Adam but there was no real difference when I tested the lightened flywheel and Eurosport clutch. That car was about as rowdy as you can build an 8v and stock was perfectly fine. You autcrossing in south bend this year?

xflowgolf wrote: I think question #2 is more important now. Is a mk1 GTI even reasonably competitive against other cars that class against it built in the last 35 years? I really don't know the answer to this. Different strokes for different folks, but it seems a bit silly to not mod a car for your own enjoyment the way you want to, if it's something that could never be competitive within it's class anyways.

Judging by the results for recent years of the SCCA Nationals the majority of national level drivers in STS are driving CRXs, EF Civic hatchbacks, and NA Miatas. So I wouldn't necessarily being outclassed by newer, more capable cars. It's not like I'm running against a Mini Cooper S, Fiesta or Focus ST, etc.

I agree that it's silly to hold back on changes I want to make to the car just for SCCA rules, but that's kind of the nature of the beast. Like I said I just want to gain enough experience to to feel like I can assess if I'm the limiting factor or the car is before I make any changes. I mean I could do the flywheel now and end up in FSP, but then I'm possibly running against someone on R-comps with a LSD.

I think if I get to a point in a year or 2 that I don't feel like it's competitive anyway then I'm going to build it the way I want to and I'll probably even consider a 16v swap even.

chandlerGTi wrote: Jason, My car had stock flywheel and clutch, I replaced the clutch (with stock) just before I sold it to Adam but there was no real difference when I tested the lightened flywheel and Eurosport clutch. That car was about as rowdy as you can build an 8v and stock was perfectly fine. You autcrossing in south bend this year?

Thanks man, good to know! I'm kinda flip flopping between South Bend and Fort Wayne. Their scheduling was pretty bad for me to try and make the full calendar for either so I'm not really worried about points this year. I just want to gain more experience. I'll probably go to some random BMW and Porsche club, etc. events too when they fit in my schedule.