Biulding A Hybrid Gearbox For My Tt

[adrian_gti 0]

Hey guys,

I got my dimma tt back from promax at last. The boost still needs setting up as it's only reaching 6.1psi at the moment. The car currently has a mi16 gearbox that was installed by a previous owner. The power delivery is awful.

 

I was looking to get a TD gearbox but my gearstick is lift up reverse and the TD is lower right so I think I would have to change linkages too?

 

Anyway to get round that problem I was thinking of building a hybrid that would give me what I need.

 

1. quick acceleration with good traction.

2. nice power delivery around 50 - 90mph

3. good fuel economy and minimum screaming from the engine at cruising speeds. 70mph on motorway and 100+ on my private road

 

Here is what I filled in for the "Table 3".. reason i put 6000rpm is the turbo has run out of puff by then so no point going above that.. hope its correct

 

to save looking at loads of diff threads here are the gear ratios for loads of boxes:

 

here is the chart with the mi16 gearbox on my TT now:

 

here is the chart from my other TT that had a 1.9 box:

 

I have a couple of ideas for a hybrid box.

The first is taking 1st 2nd and 3rd from the 1.9box and 4th and 5th from the mi16 box (same ratios as diesel) and keep the 1.9 final drive. This would give me:

 

The second idea I have is 1st 2nd 3rd and 4th from the 1.9 box 5th and FD from the diesel box giving me:

 

I know i wont be reaching the crazy top speeds but I would like 5th to be a cruising gear.

What do you guys think about the 2 hybrids above? Do you think another combination would be better suited?

 

I have a spare 1.9box and dont mind butchering the mi16box.

 

Cheers,

Adrian.

[Sandy 189]

If I were you i'd just put the Mi16 5th on the 1.9 box and leave it at that; minimal hassle (not a strip down job changing fifth) and good spread with nice tall fifth.

[TEKNOPUG 3]

Itll wheelspin in 1/2/3 with even the 1.9 gears.

 

Id keep the 1.9 box and fit a taller final drive either a diesel or turbo-diesel.

That way you keep the long 1&2 for could traction (and 0-60 without changing into 3rd, if you are so inclined) and then close-ratio 3/4/5 for mid/top punch; just a little taller in each. The TD makes the gearing 10% longer, the diesel longer still. I couldnt find a diesel box at the time of my rebuild so I used a TD FD. 80mph has dropped from 4k in 5th to about 3.6k

Top speed is over 140mph now. If you are planning torque in excess of 200lbs/ft then it may be worth searching out a diesel FD. Depends how you drive the car I guess. You will lose a little acceleration if you lengthen the gears but then you will stay on boost longer before having to change up. Horses for courses I guess and other clichés..

[adrian_gti 0]

thanks for the comments guys.

 

that could be a cheap quick way sandy thx... traction still worries me a little though..

 

Here's what it will look like with a 5th from mi16box.

 

Here's the 1.9box with a diesel FD:

 

Is it a gearbox out job to change the final drive?

[Sandy 189]

Yes, the final drive means changing the secondary shaft, so it's a complete dissembly job. Given the minimal difference the diesel FDR will make and the fact that rebuilt boxes invariably don't operate as quietly or smoothly as untouched ones, I really would be inclined to do what I suggested, it's so easy and quick. Surely you can modulate the throttle enough in 1st and 2nd to get traction? If it's that bad the suspension set up should be examined.

Edited October 16, 2006 by sandy309

[adrian_gti 0]

Your idea would be perfect if only I could get a few more mph out of 2nd gear so that I could achieve 60 before the turbo is out of puff..

 

Your idea would be free for me to do so I will do it anyway until I get my hands on another box or another idea.... the mi16 box at the moment really is terrible

[TT205 42]

I tried my TT with 4.4 final drive when I was sprinting it and it felt fabulous - BUT it was slower!, you need the longer ratios to make use of the torque that the turbo give's you.

 

I agree with Sandy - either stick with a 1.9 box and FD, put an Mi16 5th in if you really want but you really don't need one. I would only put a lower (than a 1.9) final drive in if you really are going to hike the boost up

[TEKNOPUG 3]

I just found that it went through the gears too quickly on the standard 1.9 box. With peak power at less than 6k you have to change gear far too early, before you can really take advantage on all the torque. And it would easily light up the wheels in 3rd on full boost. For manic acceleration in a straight line it was great but not good for making rapid progress A-B on proper roads.

[adrian_gti 0]

i agree with teknopug... on a dry straight road the TT with 1.9 box is great but as we all know in the uk the roads are not always dry and I dont always want to put my foot down (hence the low ratio 5th gear).

 

For now I think I'll stick the 5th from the mi16 into the 1.9 until I can source a diesel gearbox. Then I'll put the FD in too. Car is booked in Thursday to have the mi16 5th put on the 1.9box.

 

This is how it would look...

 

 

just over 65 in 2nd. 5th gear will come in on 4249rpm so shouldnt be too bad.... 70 is 2642 so this is a nice cruising rpm and should reduce the heat as the turbo isnt going hell for leather.

 

i wonder what speed the engine will actually push the car to? even though the car feels rock solid and the tyres are high speed tyres I dont think I would feel safe doing anything over 130ish.

 

has anyone else had experiences with any other ratios?

[tom_m 0]

off boost crusing means it won't get up and go if you put you're foot down.

 

1.9 box and diesel FD looks the best bet to me, on boost at cruise so you keep it on the boil and ready to work all the time... if you cruise at legal speeds that is - that and thats one hell of a jump from fouth to fifth, would probably make it more of an overdrive gear than 5th i.e. unuseable anywhere except the motorway

 

whats the rpm of the box above at 80?

Edited October 17, 2006 by tom_m

[TEKNOPUG 3]

Acceleration in 5th on the standard 1.9 box is electric. 80mph is 4k so you are bang on full boost. 80mph-110mph is just a few seconds. Great for when idiots in expensive cars are tailgating you. However, its tiring cruising at 4k and it guzzles the petrol on motorway journies. That was one of my main reasons for wanting a longer box. I didnt want to lose the superb gear spacings that the 1.9 box has though. Hence the FD change.

 

With regards to top speed (on my private test track) 6k is 132mph. Car gets VERY hot is you run this for any length of time as the turbo and exhaust are only a foot in front of you by the bulk-head. Have had it over 140mph before (6.5k) although Pug speedos arent exactly reliable (just calculating speed by revs, which is also inaccurate) this was only for about 10 seconds whilst I followed a Bentley Coupé and got sucked along behind it. Youre always gonna lose out to Mi16s as they can rev to 7.5k+, whereas youre pushing a turbo to get to 6.5k. But if you had a long enough 5th gear and suitable torque (200lbs/ft+) then Id imagine 150mph should be possible. Aerodynamics probably wont allow anymore without big power.

 

As to whether it feels stable: as long as your suspension and tyres are in good nick and brakes are sorted its no real concern. Obviously is you crash, youre brown bread. But youll probably end up Pete Beale if you crash over 60mph in a 205.

[Henry Yorke 269 3 Cars]

My CTI turbo runs an Mi16 box with a 1.9 final drive. This makes it pretty long (approx 3k at 70mph) which suits my low pressure turbo application perfectly. Cruising on the motorway is so relaxed, but with enough poke to pull you along should you need to plant the right foot!! I did have the standard 1.9 CTI box (similar to the 1.6 box) and it was god awful to drive as it just wheel span up everywhere and revved its knackers off at 4k on full boost at 70 mph

[petert 554]

If you're going to change the final drive, I'd also consider lowering 1st, using the 3.25:1, or even a 3.45:1. Otherwise it will be a dog to get get off the line when there is no or low boost.

[cybernck 400 1 Cars]

i think that's a good and relaxed choice for a turbo'd 205, especially if you're planning on power increases.

[pdd144c 0]

Have you got a LSD? Plated LSD or ATB diff will really improve matters. I could launch my TT of the line with next to no wheel spin when I had one fitted. I ran numerous boxes on mine for a while, and then went back to standard 1.9 internals with the ATB. By far the best option in my opinion.

[TEKNOPUG 3]

Yeah, I have a Quaife ATB and that's made a big difference.

 

Petert: 1st is long and second too. Certainly the FD change has effected this two gears the most in terms of performance. I do have a lightened flywheel though which helps the engine spin up so it's not a real everyday problem. Only perhaps when you're doing standing starts and traffic-light GP's. The improvement in 3/4 (where most driving is done) far outweight this.

[adrian_gti 0]

I dont have a LSD yet but was planning on getting one over the next few months... is this something I should do before the gearbox? Do they have to remove the gearbox to put a LSD on? Would make sense if i do it now if thats the case.

 

I managed to get a diesel box and it might be delivered today / tomorrow.

 

I was thinking about what petert said about getting off the line when there is no boost. The car also has a lightened flywheel so revs nice and free but maybe it would be a good idea also using the diesel 1st gear.

 

Here is the chart using diesel 1st, 5th and FD and 1.9gti 2nd 3rd and 4th:

 

 

it also shows rpm at 80mph and 90mph.

 

the rpm when changed into 2nd is almost the max torque so should give pretty good accelearation up until i change to 5th.... then the race is lost

 

If the gearbox needs to come out to do the LSD then I'll put a hold on everything until I have one... wheres the best place to get one? Sorry I'm not too clued up on these things

 

Cheers.

 

edit: Teknopug.. can I borrow your private test track please

Edited October 18, 2006 by adrian_gti

[TEKNOPUG 3]

Yeah, the box needs to come off to fit the diff. A Quaife ATB diff is probably the best for the road, as its fit&forget. Doesnt require any adjustment or maintenance. I think that they are £495+vat. Best thing to do is get the gearbox, the diff and the gears/FD you want fitted and send it all off to Miles to rebuild for you.

[Henry Yorke 269 3 Cars]

Best thing to do is get the gearbox, the diff and the gears/FD you want fitted and send it all off to Miles to rebuild for you.

I'd second that. Or if you are even lazier, jut tell Miles what you want and he will get all the bits as well!!

[adrian_gti 0]

bah all the parts are now in the back of my car. Promax are my new best friends and are going to do the gearbox.. no doubt it will be expensive but I know they wont mess up... hopefully

 

I'll give them the garbox to rebuild with new ratios but wont have it installed until I can get a LSD prolly end of month or mid next month

 

Am I right in saying LSD will help me go round corners quickly? Is there anything I can check to see if a LSD has already been put on as the car goes round corners and handles a lot better than any of my other 205s.. would hate to buy a LSD not knowing I already had one. maybe promax will know?

 

thanks for all your help guys

[TEKNOPUG 3]

bah all the parts are now in the back of my car. Promax are my new best friends and are going to do the gearbox.. no doubt it will be expensive but I know they wont mess up... hopefully

 

I'll give them the garbox to rebuild with new ratios but wont have it installed until I can get a LSD prolly end of month or mid next month

 

Am I right in saying LSD will help me go round corners quickly? Is there anything I can check to see if a LSD has already been put on as the car goes round corners and handles a lot better than any of my other 205s.. would hate to buy a LSD not knowing I already had one. maybe promax will know?

 

thanks for all your help guys

 

 

You should notice whilst driving: if you go into a corner too fast and start to understeer and then just when you think you are going to lose controls, the car suddenly pulls round the corner like its on rails, you have an LSD fitted. If your car starts to understeer and you keep on the power and it continues understeer, then you dont.

 

Alternatively, jack up the front of the car. Turn one front wheel by hand, if the other wheel turns at the same time, you have an LSD fitted. If it doesnt you dont.