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Paddy1970

Project Valtezza

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Thanks for the feedback on that chaps, I hear what you're saying about going too wide, the plan is 245/45/15 on the rear and 215/50/15 fronts. The car won't be driven in anger in the wet but I would like a decent level of traction in the dry and I know from experience with this particular engine that a 245 is the bare minimum requirement, granted in an Mr2, not a Hood, we have weight over the rear wheels with those.

 

Hey i'm very open to your advice, it's my first major seven project but far from my first rodeo.

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Personally dont see there being a need for more than a 195 upfront, but then as you have 9 inch wide rims, theres no way you could fit a 195 to that, you'll already have "stretch" with a 215.

 

245 on the rear may be ok, but is certainly very wide, and if you found a lack of traction on the rear end I would look at reducing width rather than increasing!

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Realistically it'll all be in the compound of the tyre and the compliance within it, along with your driving style and what you're after. Look at a 620R, it gets away with 185's on the front and 215's on the rear. That should tell you all you need to know :).

 

With wide tyres there's theoretically more rubber to intereact and adhere with the tarmac, but there isn't a simple, clear formula for calculating what you need. So a lot of it will be feel and experience from others doing the same out there. We had 205's on the back of an Exmo with only 130bhp, they weren't a high grade tyre and I don't think the experiences I had with it will really help in your case. A lot of manufacturers run wide tyres more as a compromise towards wear rates, heat management and ride quality (you can ride over small potholes with no effect, for example). It's not always about grip. I'd be concerned that a 245 on the back will spread the contact patch so thin and wide that you might get good transverse grip off the line but the cornering grip might be a bit "skittish"... again, assuming all else is equal in terms of tyre compound and tread pattern/etc. I know some old Dax Rush's that used ridiculous sized rear tyres back in the 90s, one mate took me around Donnington in it... all 310bhp of it. I then returned the favour and took him around in our little Exmo and he was shocked (in a good way) at how much grip there was, considering it was running on pretty poxy Pirellis and the horrendous suspension that comes with it.

 

Give it a go, certainly it will look nice, I wouldn't go any wider than those numbers though, unless you're happy for it to be more "show" than "go", if you know what I mean?

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The 620r uses avon zzr tyres......Avons own website says that effectively they are race tyres,

with mods to make them road legal.

http://uk.caterhamcars.com/cars/seven-620r

http://www.avonmotorsport.com/road-legal/performance/zzr

 

So compound seems to be more important than size

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I will see how it behaves on my planned tyres and go from There.

 

I made a start on the new plenum which needs to sit much lower than the original and also relocates the throttle body to the rear of the engine.

 

I've started by cutting the lower flange off the plenum, this will form the starting point for it.

 

YZXWWFC.jpg

 

imilnJw.jpg

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Coded welder, Paul? very pretty -- most of my welding needs "fettling" with the angle grinder.

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Thanks, no I'm just self taught and been welding all of my life, started oxy-acetylene at 16, Mig and stick for the last 30 years, started Tig welding about 5 years ago.

 

Aluminium is my favourite but can be very hit and miss, even though I've been welding all of my working life I still feel every day is a learning curve.

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Plenum lid on and throttle body mocked up in position....

 

lzqq5jO.jpg

 

Throttle flange tacked on and more sections added...

 

ZG8UMgT.jpg

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Is that shape not going to affect the airflow into the individual runners detrimentally?

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More than likely, I have no other option to be honest, I need to get everything under the bonnet and this is the only design that will work.

 

It's not ideal, I might lose a little torque somewhere but luckily it will have more than enough anyway.

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Have little idea of air flow --- but could a floor to ceiling baffle ( of the air box) on both sides of inlets -- open at each end help? Pressure would then be "balanced" with the air entering at both ends ?? :nea:

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Not sure to be honest, i'm no expert on flow dynamics etc, i've just tried to copy the same volume of plenum that it had before, which was roughly 1ltr of plenum. I have 35mm x 400mm x 300mm, plus the tapered intake part which gets me to around 0.8ltrs, so i'm in the right ballpark volume wise, flow we shall have to see once it goes on the dyno, might have to force a pair of small turbos down its neck :)

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First wishbone underway, I made the jig out of an old kitchen cabinet door. 30mm CDS tubes used throughout.

 

This jig will allow the other front lower wishbone to be an exact copy of this one, I still need to make jigs for all of the other wish bones though.

 

Chev5YE.jpg

 

7koIcjL.jpg

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