405 Mi16-6 - a GTI-6 gearbox conversion

[Guest P Zero]

So was it worth it? I think I'll need to have some work done on my current box but if theres a definite advantage to using the six speeder then I'd consider tracking one down.

[KRISKARRERA 2 1 Cars]

Definite advantage at intermediate speeds but less so accelerating from a standstill because 1st and 2nd are longer than Mi16 box.

[Sloppy 0]

I toyed with the idea of getting a GTI-6 engine and box to put in mine when it was engineless, but decided to keep with the Mi16 engine in the end. I'll be interested to hear how well suited the ratios are to the Mi engine in a 405 when you've got it sorted

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i thought the mi16 engine was although less powerfull much more tuneable due to the fact it has bigger valves and massive valve seats giving the potential for VERY big valves to go with cams and a remap to make BIG power, however the gti engine/head does not have this same asset. a guy on pumaracing.com does head works and explains it in detail.

[cybernck 402 1 Cars]

GTI-6 head is a lot better, valves have 6mm stems instead of 7mm on the Mi16

(for yet better flow) and valvetrain is a little bit lighter too. all-in-all, GTI-6 engine

is like a more modern and improved Mi16 engine.

[Guest P Zero]

So, back to the 6 speed box. If I were to customise one, am I right in thinking that by replacing 1st and 2nd with Mi16 items I would end up with quite a good replacement?

[KRISKARRERA 2 1 Cars]

Sadly not because it's the final drive that's low on the mi16 box. A gti6 box with an mi16 final drive would be fantastic but it's not possbile.

[Sloppy 0]

GTI-6 head is a lot better, valves have 6mm stems instead of 7mm on the Mi16

(for yet better flow) and valvetrain is a little bit lighter too. all-in-all, GTI-6 engine

is like a more modern and improved Mi16 engine.

<{POST_SNAPBACK}>

 

but surely this limits the size of the valves or the potentail size in the gti head, the dude who works on heads from puma racing is adiment the mi16 head was more designed with bigger power and flow in mind hence his extensive work to mi16 heads for large power increases compared to the git one.

 

Ha ha improvement, the snap cambelts for fun, persoanlly i think the under engineered as they seem to be plauged by cambelt failures even under very low mileages like 35k...

Edited May 27, 2007 by Sloppy

[Baz 421]

and Chocolate-like pistons!

 

I guess it's a trade off between having a lighter engine but with possible surge /starvation issues or a better flowing heavier engine that like to melt pistons and eat cambelts...

 

The cambelt issues aren't so bad if servicing is kept on top of surely.

[Guest pugmt]

Sadly not because it's the final drive that's low on the mi16 box. A gti6 box with an mi16 final drive would be fantastic but it's not possbile.

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Back to this but anything is possible, just depends how much money you want to spend acheiving it. as it is only the layshaft (secondary shaft) that is diferent, all you would have to do is have this shaft made up with a different pinion gear cut on the end to match the crown wheel of the MI16 one. Like i say all it comes down to is cost..

[Sloppy 0]

and Chocolate-like pistons!

 

I guess it's a trade off between having a lighter engine but with possible surge /starvation issues or a better flowing heavier engine that like to melt pistons and eat cambelts...

 

The cambelt issues  aren't so bad if servicing is kept on top of surely.

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Ha ha you cant win!

 

i dont rate the gti engine, the amount of people who have cambelt issues and tapping head and conrod faliures is crazy, although like you said if you ghet a good one there are very quick, my bro had a nice w reg one and he drove it very hard all the time with enthusiastic mantainence and it never had any faults what so ever...

[Jer309GTi 3]

Can we keep this on-topic please...

 

Sadly not because it's the final drive that's low on the mi16 box. A gti6 box with an mi16 final drive would be fantastic but it's not possbile.

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Back to this but anything is possible, just depends how much money you want to spend acheiving it. as it is only the layshaft (secondary shaft) that is diferent, all you would have to do is have this shaft made up with a different pinion gear cut on the end to match the crown wheel of the MI16 one. Like i say all it comes down to is cost..

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As a one off this would be expensive, right? But if an engineering company had a pattern of the modified seconday shaft that you talk about then maybe a batch could be made for a reduced cost? Not too hot on gearboxes and their components, just trying to get an idea

[Guest P Zero]

As a one off this would be expensive, right? But if an engineering company had a pattern of the modified seconday shaft that you talk about then maybe a batch could be made for a reduced cost? Not too hot on gearboxes and their components, just trying to get an idea

<{POST_SNAPBACK}>

Forgive my ignorance as I am not familiar with the parts being talked about, but I assume its not possible to modify the shaft without seriously sacrificing strength?

Edited May 28, 2007 by P Zero

[Jer309GTi 3]

Good question! I would have thought it would have made the shaft weaker, but then again I'm no expert

[Guest pugmt]

You don't modify the existing shaft, but you have a new one made to the specifications you require, I.e. copy the 6 speed shaft but with the cut of the mi16 pinion gear on the end of it instead of the gti6 one. yes one off's are expensive and yes the more you have made the cheaper they become, but it is question of how many people would cough up the readies before they get the parts, as most small batches of parts have to be part paid up front. If enough people express an interest i will do the finding out as i was looking at this for myself anyway.

[Guest P Zero]

I'd definitely like to find out if its affordable.

[KRISKARRERA 2 1 Cars]

I seem to recall from speaking to Miles ages ago that it was something crazy like a grand. I was really thinking about this for if I get a 306 GTI6 some day.

[Guest P Zero]

 

Most of us spent that much on our cars!

[KRISKARRERA 2 1 Cars]

Well yes exactly though I can't be 100% sure it was that much, was so long ago I asked him. It was enough to put me off doing it though lol.

[Guest P Zero]

erm, I think I can see why.

[PugMi16 0]

I gain big acceleration putting gti-6 gearbox since i found out that my old gearbox wasn't from mi16 but from Sri, so I cant tell much is it better than mi16 gearbox since i never had one on my car

[Guest Skeleton]

I would say your best bet would be to use the BE3/6 if your also going to transplant a Xu10j4rs into it aswell. The engine has more torque and it layed out over a wider band compared to the Xu9j4, by design BE3/6 is more suited to that. Unless your running a modified Xu9j4 to produce similar torque layed out over the rev range then there is no real big advantage to using the 6 speed. If your going to bother installing a BE3/6 then it makes sence to match it to the block it was designed for.

 

 

As for pumaracing prefering to work on the Xu9 over the Xu10 is in my opinion due to the alloy block being easier to machine and work on. As for the big valve convertions.... Unless your wanting 280 hp, a giant hole in your wallet and a engine under ALOT of needless stress, there really is no big advantage of the big valves. Sure it can have great results if your building a racing engine. I doubt it would be very joyful to drive on the street. Wat ever happened to good old simple high comp pistons and cams?

Edited September 7, 2007 by Skeleton

[Guest turbolag]

Other problem with big valves is the greater mass creates higher inertial forces and you're more likely to end up dropping one. Ouch!

 

Not a huge drawbak, but one to consider. It's the sort of mod you've really gotta want. Nitrous'll give you more shove, for less outlay and less risk, albeit about as practical as hiring Jade Goody as an image consultant.

[PugMi16 0]

I have a problem since i'v putted the gti-6 gearbox. my alternator scratcess the chasey when i'm going to left corner with full gass. Since the gearbox is too large too fit I'v moved whole engine to the other side for some 1-2cm. For any kind of solution for this scratching I would be thankfull

[Guest badboyracer3500]

I have a problem since i'v putted the gti-6 gearbox. my alternator scratcess the chasey when i'm going to left corner with full gass. Since the gearbox is too large too fit I'v moved whole engine to the other side for some 1-2cm. For any kind of solution for this scratching I would be thankfull

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When ever i've spoken to people about this mod, i'm told that a piece of the chassis has to be cut out and plated up to allow the box in. This then does away with moving the engine over.

[PugMi16 0]

I have a problem since i'v putted the gti-6 gearbox. my alternator scratcess the chasey when i'm going to left corner with full gass. Since the gearbox is too large too fit I'v moved whole engine to the other side for some 1-2cm. For any kind of solution for this scratching I would be thankfull

<{POST_SNAPBACK}>

 

 

When ever i've spoken to people about this mod, i'm told that a piece of the chassis has to be cut out and plated up to allow the box in. This then does away with moving the engine over.

<{POST_SNAPBACK}>

 

I did cut the chasey to fit the gearbox but still I'v had to move the engine so that I can have a full wheel turn. So the tire isn't scratching the gearbox but engine scratches the chasey