gettng as much BHP from my mk3 gti 16v as poss

[Adam]

Bike carbs are the way forward 

[Ess_Three]

Bike carbs are the way forward 

Surely going to any form of carb from proper engine management is a backward step?
ITBs would be a way forward though.

[Adam]

Bike carbs are nearly the same as itb tbh.

[Ess_Three]

Bike carbs are nearly the same as itb tbh.

...except they are a carburettor, not an individal injector body, and as such are never going to give you such fine control of the engine...and you can't run them easily with a cat, or with cold start mapping.

Better off with bike ITBs instead, from my experience...and even then you have the problem of not ideal throttle openings and restricted injector selection...but easier to get the fuelling correct than using bike carbs.

[Adam]

Bike carbs are nearly the same as itb tbh.

...except they are a carburettor, not an individal injector body, and as such are never going to give you such fine control of the engine...and you can't run them easily with a cat, or with cold start mapping.

Better off with bike ITBs instead, from my experience...and even then you have the problem of not ideal throttle openings and restricted injector selection...but easier to get the fuelling correct than using bike carbs.

You do know your stuff, ex-VW master tech? 

[Ess_Three]

You do know your stuff, ex-VW master tech? 

Nope, my mate is a VW Master Tech though...

I'm just an interested fettler who's spent/wasted thousands on 'stuff' to do with cars.
It's a hobby. That's how I justify it....it keeps me out of the pub!

[Paul86S2]

...and you have a driveable car which is fast enough for most road conditions.

Here's a thing:
Instead of chasing BHP that a lardy Mk3 is struggling to make best use of...why not do something that will actually make it substantially faster point to point (but not have the todger-fencing bragging rights in the pub)

Change the hopeless FD ratio it came saddled with (although not as abysmal as the VR6) to a 3.94 to get the gearing down to around 20 MPH/1000revs in top...lovely!
Fit a light flywheel - and instantly feel like you've added 40 BHP
Fit a Quaife diff and re-learn cornering ability...

Good info as always. How hard / expensive is it to change the final drive?

If you were using 205 50 15 tyres wouldn't changing them to something like 195 45 15 tyres have a similar effect. Some quick rough calculations show a similar change to the gearing (presuming I haven't missed something glaringly obvious).
I'll try to find the gear ratios and put them into an online calculator.

Hows the Jenvey throttle body and megasquirt conversion coming on?

Cheers

Paul

[Ess_Three]

Good info as always. How hard / expensive is it to change the final drive?

Cheers Paul!
Not easy to change the FD. It's a gearbox rebuild to do it...but since many will have a 2nd-3rd crunch by now anyway...it's the perfect time to do it.
You are probably looking at around £500 rebuilt with a new FD.
About what it costs to fit a pair of cams...and it'll make the car better than the cams ever will!

Of course, start adding a Quaife as well and it easily adds another £1000 on top.

But still comes in around the price of a decent re-worked head and cams...and will be the faster A to B.

If you were using 205 50 15 tyres wouldn't changing them to something like 195 45 15 tyres have a similar effect. Some quick rough calculations show a similar change to the gearing (presuming I haven't missed something glaringly obvious).
I'll try to find the gear ratios and put them into an online calculator.

Yup, that would work...
Or 215/40/16 Anni size...that's about as low as the Mk3 ever went, gearing wise. And you get the extra width related grip too.

Hows the Jenvey throttle body and megasquirt conversion coming on?

Getting there...
Jenveys are now re-worked into 8 injector spec (4 hung over the bellmouths for pre-mixing!) and i'm in the final stages of fabrication for the EDIS ignition. I was pretty much there...but decided to change the ECU and run it fully sequential on the primary 4 injectors, so needed to keep the std dizzy's cam position sensor...so all my brackets and bespoke HT leads won't fit any more (30mm too short) so I'm still getting back to where I was on that.

Jenveys are built, with linkage, rampipes, spacers twin fuel rails and FPRs, filter backplate and dome filter - which look like they'll clear the Mk3 bonnet with feeler gauge clearances!


MS has been removed as it still needed a vacuum signal for it's MAP sensor...and that's what was causing me grief with my cams and the standard plenumn...so it's out.
I just need to re-solder the plugs on and punt it on as a complete, mapped MS that plugs into a standard ABF ECU connector - plug and play!
(need to pull my finger out there...I only removed it last week...after it had sat unused for a year or so!)

I've gone with Emerald K3Pro instead...complete with full throttle gear shift capability, 8 injector capability etc.
Nice!
I'll be able to re-install my nemesis then (Schrick 268 ex cam!)


So there you are...all my 'secrets' out of the bag, as it were!

I have a renewed interest in getting the GTI finished (if there ever is such a point) after GTI International this year.

[Paul86S2]

Ess Three

Thanks for the info.

Looks like the differance between the 205 50 15 and 215 40 16 diameters isn't that great but the 195 45 15 diameter will give a similar effect to changing the final drive.

If I am right with changing the final drive you will get faster acceleration but lower top speed in each gear. I need to work out if changing up to 5th on some tracks will be beneficial, or whether slightly slower acceleration but staying in 4th will be better.

Obviously on slower tracks it will be of benefit, but at Castle Combe and Goodwood we are just starting to hit the limiter at the fastest point before braking. Not sure going into 5th will be of real benefit.

Sounds like you are getting there with the ITB project. Lets hope you get to break your magical 200 bhp barrier and get that exhaust cam working that has been giving you grief.

As far as the MS system goes do you think its of benefit over the normal ecu system on a fairly standard tuned car or only worthwhile to make use of major tuning upgrades?

Cheers

Paul

[Ess_Three]

Ess Three

Thanks for the info.

Looks like the differance between the 205 50 15 and 215 40 16 diameters isn't that great but the 195 45 15 diameter will give a similar effect to changing the final drive.

You could be right...
I seem to recall 195/50/15 and 215/40/16 are both similar, and both lower than 205/50/15.

If I am right with changing the final drive you will get faster acceleration but lower top speed in each gear. I need to work out if changing up to 5th on some tracks will be beneficial, or whether slightly slower acceleration but staying in 4th will be better.

Spot on.
Lower speed in each gear, usually offset by higher rev limit from tuning (cam and mapping etc).

Technically, a lower top speed too...although lack of power and aerodynamics will stop play long before you hit the rev limiter in top on a Mk3 anyway, so hardly an issue.
I can pull 6800-7000 in top in my ABF with 3.94. Rev limit is 7300. That's it...too much drag for any more
With a 4.2 I'd hit the limiter in top.

Obviously on slower tracks it will be of benefit, but at Castle Combe and Goodwood we are just starting to hit the limiter at the fastest point before braking. Not sure going into 5th will be of real benefit.

Possibly not...you may have to hold on the soft limiter...saves changing up and straight back down again.
The lower FD brings the Mk3 alive.

Sounds like you are getting there with the ITB project. Lets hope you get to break your magical 200 bhp barrier and get that exhaust cam working that has been giving you grief.

I'm confident... 

As far as the MS system goes do you think its of benefit over the normal ecu system on a fairly standard tuned car or only worthwhile to make use of major tuning upgrades?

MS doesn't have the same perfect idle control as Digi 3.2, that's for sure.
Everywhere else, you'd not know it wasn't Digi 3.2.

The main advantage, is that you have total control over the timing and fuelling. So each time you tweak something, it saves you £350 in getting a bespoke ABF re-map done...just head to the dyno for an hour with your laptop.

Great for changing cams, filters, head, TB etc...

Mine was properly plug and play into an ABF - uses all the standard sensors, and fires standard injectors, so once installed you'd not know it was there...except for the less than perfect idle mapping as I never spent enough hours refining that...oh, and it has launch control too!

Does a standard ABF need standalone management?
No.
Will you get any gains over a re-mapped Digi 3.2 ECU?
No.

Will it let you play to your hearts content and map for all modifications...hell yeah!
It takes some time to learn the software...but once there you can on the fly map, using the standard narrow band lambda and 'Megatune' application to get it close...then just do the on-load mapping on the dyno. All for less than a generic re-map.
And it's there for any other mods you care to add.