16V Unmodified Intake Vs Single Carb Unrestricted

[MrButler_1 0]

Hi everyone, first post so apologies in advance for my lack of technical knowledge but I'm really struggling to get my head round something so I hope I might be able to get some insight here with the help of some experienced people.

I have zero practical experience, just a lot of internet research time and a thirst for knowledge and I'm embarking with a mate into a bit of casual motorsport, predominantly road rallying and some hillclimbs etc.

We haven't got the car yet as we're researching what's going to best for our needs first so that we have a solid plan but we've whittled our choice down for now to either a 205 or perhaps a 106 so exploring the options in further detail, and looking to get the maximum tunability/power within the regs.

Road rally regs state:

SOHC ONLY unless engine was originally a fuel injection and the F.I. including plenum and T.B. remains unmodified. (So you can have 16V but can't modify the intake)

FUEL INJECTION not permitted unless it was original to the engine and remains unmodified as above (so you can have F.I. but can't modify the intake and therefore cannot for example put a 16V head on an 8V engine)

MAX 2 CHOKES - either 2 single or 1 double so no twin 40's etc.

What I'm stuck on is which combination would be best? If using fuel injection then may aswell have 16V because the rules are the same for both (i.e/ no intake mods) but would this be better than an 8V with a single (double choke) large Weber 40/45/48 for example (as no restriction on carb size). From researching though, it seems that such a manifold does not exist for a 205 and one would have to be made up. I have no idea how much that would cost, how reliable or functional it would be as I'd imagine there's quite a bit involved in engineering the correct flow to the cyclinders. Being a kid at heart, I can't help thinking the latter would feel and sound more like a rally car! If it doesn't, well that's half the fun taken out

All this affects which engine we would go for, either 1.6/1.9 GTI 8V or MI16 or GTI6 16V and obviously each one has different cost considerations. Looking at ultimately tuning whichever engine we decide on to the maximum subject to affordability and regs so aiming to have headwork done, pistons, rally cam(s), exhaust etc and have a screamer.

Thanks for any thoughts and opinions...

Edited May 24, 2017 by MrButler_1

[Tom Fenton 1,524]

Tbh you are barking up the wrong tree. To begin with focus your spending on dampers, brakes and a limited slip diff, and focus your attention on whoever is navigating.

 

Outright power isn't really what's needed, a standard car will show up issues as mentioned on the rougher stuff far before you need more power.

 

A decent navigator will also make the difference between enjoyment and frustration!

[Tom Fenton 1,524]

Just to qualify, I've been at it as a navigator 5 odd years now. (Road rallying) It's a fantastic bit of sport, the navigator can really make the difference.

If starting with a 205 then you need a substantial sump guard. Bilstein challenge dampers all round a good start. As a minimum some good Mintex/Ferodo pads in the standard brakes but ideally something bigger.

Start off doing club events, 12 cars scatters whatever they run. Good for learning the ropes.

[MrButler_1 0]

Hi, thanks for your response. We can assume that dampers, brakes, LSD and everything else has already been modified to the maximum subject to the regs and without going silly on the cost. I'm looking at the engine in particular here as we want a quick car and to be reasonably competitive in road modified hillclimbs. Navigator is very good...

[allanallen 528 2 Cars]

Assuming you're running APs, proflex and a plated diff I'd keep the standard inlet manifold and throttle body, but fit some hotter cam/cams and aftermarket management, oh and a shorter final drive. With a pokey engine a 1900 box with a 4.4 would be ideal.

 

If I was to build another road rally 205 I'd fit a standard 6 engine with a 1900/4.4 gearbox combo and spend the rest of my budget on rear dampers. Other than launching out of SGW loads of power simply isn't necessary.

[Miles 331 1 Cars]

Huge difference is reg's, as Tom's said Power is not the end all in Road Rallying but a engine tuned to the full allowable reg's won;t be competitive in Sprints, Example my 306 has over 250bhp and is Road going so really 2 car's or 1 class

[MrButler_1 0]

Cheers for the comments, all good stuff...

 

Realistically we'd be happy just being in the mix for the hill climbs against other similar 205's. We wouldn't be doing it very often so it would be just for the crack but at the same time we'd like to be as quick as we can be. Last months local for example had 5 205's in the class out of 12 cars. Only main difference in the regs is that induction is free for hill climbs hence my question about the best intake solution.

 

Another requirement is that the engine block must be externally identifiable as that of the originally fitted type for the car but a lot seem to be getting away with running MI16's, although technically they should be put in another class. Strictly abiding by the rules in order to enter the road modified production class we'd have to run a 1.9 XU but then it would have to have an 8V head due to road rally regs. I get the impression a GTI6 engine might be taking the mick a bit so really it's probably more between a 1.9 8V or MI16. Either way, do you reckon aftermarket mapping would trump a single (double choke) carb setup on a 1.9 8V? I'm guessing an MI16 would top that aswell but there's a moral dilemma with running that! Cheers

[allanallen 528 2 Cars]

A double choke carb set up is a backward step from the original injection system. The manifold will be the biggest issue as its design will always be flawed.

As miles says you're trying to fit a car into 2 classes with different regs. An mi16 is the obvious engine choice

[MrButler_1 0]

Thanks, will pursue the MI16 further then and research more into the sump issues and dry sump cost etc. I guess what gearbox is a whole separate debate but would you still go for a 1.9 4.4 box with an MI16? Is that a big costly job or not so bad? Guess that would be pretty lively and revvy with a hot cam. Read a lot that there's a big drop on a 1.6 box from 1st to 2nd although its shorter so I like the sound of the shorter final drive on a 1.9 box. Plus it would mean we can concentrate on sourcing a 1.9 as the base car. Cheers

[steve@cornwall 100]

You ruling out a 309? Factory 16v was made

[MrButler_1 0]

Yeah, not the biggest fan of the 309 tbh. Love the 205's too much

[Miles 331 1 Cars]

Most high powered 8v's use Mi blocks and unless you know what to look for they are pretty much the same, The later 8v blocks where different again so I;ve never known this to be a issue over 30 years

[MrButler_1 0]

Apologies Miles, I don't quite understand. What have you never known to be an issue? Cheers

[barneys66 120 1 Cars]

Is that a big costly job or not so bad? Guess that would be pretty lively and revvy with a hot cam. Read a lot that there's a big drop on a 1.6 box from 1st to 2nd although its shorter so I like the sound of the shorter final drive on a 1.9 box. Plus it would mean we can concentrate on sourcing a 1.9 as the base car. Cheers

I have the 4.4 FD in my box, albeit behind a modified is 8v, and it's great. The obvious penalty of a reduced top speed is not an issue for me (other than country lanes I mostly do autosolos) and I guess from above it won't be for you either.

 

Ring and pinion combos come up for <£150 and allow a lazy day to convert if the box is out of the car - you'll need access to a press otherwise it's hand tools only.

 

Here's an invaluable guide for future reference http://www.rallyparts.co.uk/cwp_change/

 

Keep the updates coming!

[Miles 331 1 Cars]

Running 16v blocks as 8v's, You would really have to know the little difference's and in terms of power gain is nothing

[eastlondonpug 6]

Most high powered 8v's use Mi blocks and unless you know what to look for they are pretty much the same, The later 8v blocks where different again so I;ve never known this to be a issue over 30 years

30 years of what? Do you remember the junk block you put in my car with 3 holes that you bodged with quick steel?