Mk3 vs Mk2 - differences? more FIA HTP...

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knutspeed
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Mk3 vs Mk2 - differences? more FIA HTP...

Post by knutspeed » Mon May 12, 2014 8:51 am

We've got a heavyweight challenge...
Our Bevan tribute car has a FIA HTP as a Mk3 Imp Sport. Unfortunately, this requires it to weigh in at 716kg, whereas a MK2 Super or Singer may run at 668kg. We've stuffed the car with heavy, useless items to get it to the weight limit, but it's not much fun since the car in Mk2-spec only needs the odd 20kgs to reach the minimum, but as a Mk3 we had to weight it down to the order of a grown-up passenger. A difference of nearly 50kgs also leaves it at a disadvantage compared to everything else, of course.

I'm now looking into re-homologating the car following homologation 5016 rather than 5161 (can't see how I made the mistake in the first place with those numbers...um...). Is there any differences between a Mk3 and a Mk2 that would make this job impossible?

Oh, and the homoloation papers states 716kg as with fluids and spare wheel (!), but sans petrol.
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
FIA App K Historic Racing Imp - Bevan Tribute - www.shag.no
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by SimonBenoy » Mon May 12, 2014 11:40 am

Hi Matthew

By mk 3 I assume you mean it is a post 1969 model with the later dash. This will be the most obvious difference, also the door locks were changed on the mk 3s to the anti-burst design. Do the homologation papers go into this level of detail? If not, then it should be straightforward but if you have to swap over the dash panel, that could be a bit messy!

Our non-FIA spec cars runs at 680kg with the driver (up to 998) or 710kg (1000-1150).

Regards - Simon
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by knutspeed » Mon May 12, 2014 12:08 pm

Thanks, Simon. Door locks no problem, and it's already fitted with a Mk2 dash with Rallye Pod.

The FIA weights are ex-driver. I was quite surprised when we first checked weights when they were built. With plastic windows, boot, bonnet and no bumpers both cars were about 630 less petrol. So we had to start bolting on heavy stuff and could have dropped all the GRP and lexan...
Matthew Birger Patrick (Knutsen)
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by johnh875 » Wed May 14, 2014 4:00 am

Interesting question Matthew. Weights recorded on homologation papers don't always reflect reality, often what a manufacturer can get away with (if they are so inclined). I've not seen an Imp kerb weight as low as 668kg, not that the homologation weight is necessarily the same as 'kerb weight' which may include petrol but that still probably wouldn't make up the difference. There is roughly 50kg difference between an Imp basic spec and a Stiletto for example but that wouldn't account for the increase in homologation weights.

Are there any benefits in the latter spec compared with earlier, I've never seen any of the homologation papers as racing is to local regs here, must keep bumpers, steel panels, glass and interior trim for example, as was raced in period.

I can see how the degradation in power-to-weight ratio would outweigh any advantage in ballast weight distribution tweaking. From what I could find in 2 minutes via google it looks like the 1971 car at least had a binnacle dash, I wonder if there was an year of manufacture officially recorded for the car - but in short there probably isn't anything to say that the Bevan car you've replicated is a 1969 or later.

John
Imping (on & off) for 20+ years
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by knutspeed » Wed May 14, 2014 7:11 am

A little update - the "wrong" homologation papers state 716, but the HTP actually specifies 698 for our MK3. Still 30kgs that I don't need, but slightly better.

No big worries - the HTP now needs a renewal every 5 years (to the price of £500 and quite a bit of work & follow-up), so we might wait until it's due in a few years, or at the earliest, this autumn.

The showstopper would be if there was any major body shell differences, as with Minis for example - a Mk1 can be converted to a Mk2 and vice versa with a bit of welding, whereas a Mk3 or Mk4 have too much shell changes (doors/hinges, floor, front subframe mounts etc). Seems the Mk3 Imp can easily be reverted to Mk2.

All the homologations are the same, more or less - so our two racing Imps are idential cars save for some trim/Interior. Thing is - a Mk2 Cooper S is allowed at 607kgs, and that's our main opposition since we're running in the 1300cc class over here. 100kg more and 300cc less are a bit much, even if the Imp eats minis in the corners.
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by SimonBenoy » Wed May 14, 2014 11:26 am

Sadly, Rootes and subsequent owners didn't do us historic racers any favours thanks to the lack of homologation in period with cicuit racing in mind.

Are you allowed twin 40s or do you have to use 150 Stroms?

Of course, in period I am sure that the Imps would have been racing at lower weights than the kerb weight even when they had some interior and bumpers. But the Bevan Imp could beat the 1300 Minis - indeed they did exactly this one year, entering an Imp at 1001cc in the larger class to prevent the Mini getting the class win. Not sure what weights applied then though.

Cheers - Simon
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by knutspeed » Wed May 14, 2014 12:53 pm

Simon, yes we're running twin 40s. The engine in my car gave a healthy 117hp on the dyno, so happy with the performance. We're actually running in a FIA class up to 1150cc, so there's options there as well.

The Imp has already got the pace of the 1300 class, and had the fastest lap times last weekend. Since we're running the fat Avon ACB10s, and proper rear dampers now (alloy Konis) the car is simply incredible in the corners and on the anchors and will gobble up anything. Problem is the straights and the mickey-mouse Scandinavian tracks, where the Minis and Escort GTs will outdrag us, so getting past is a real challenge.

So we are looking at every option to become more competitive, even if there's a large chunk of lap time still stuck in the pilot :)
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
FIA App K Historic Racing Imp - Bevan Tribute - www.shag.no
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by knutspeed » Wed May 14, 2014 1:12 pm

Image

I know racing the Imps on the Dunlop Spec tire is fun, but you should really try wide boots just once....it feels like a single seater :D
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by ImpManiac » Wed May 14, 2014 2:42 pm

knutspeed wrote:The engine in my car gave a healthy 117hp on the dyno, so happy with the performance. We're actually running in a FIA class up to 1150cc, so there's options there as well.
Is that power output from 998cc? :shock: It sounds as though you have the car set up nicely. :)

IM 8)
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by knutspeed » Wed May 14, 2014 3:12 pm

I think it's a 1040cc. FIA Class limit is 1150.
Then again, there are optimistic dynos... it certainly goes well, but quite a bit off a mini in a drag race. 100kg less, 20 hp more, and a fair bit more torque as well.
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by Gaffer » Wed May 14, 2014 6:35 pm

knutspeed wrote:Image

I know racing the Imps on the Dunlop Spec tire is fun, but you should really try wide boots just once....it feels like a single seater :D
I notice the GOPRO bolted to the cage. any vids to see :?: If so, a link would be nice to see 8)
I also agree with trying an Imp on wide tyres. mine scares the life out of me :o :lol: :lol:
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Re: Mk3 vs Mk2 - differences? more FIA HTP...

Post by knutspeed » Wed May 14, 2014 7:06 pm

Hi Pete, thanks - indeed there is a video:
https://www.youtube.com/watch?v=uDQqyoj ... pOyRlvGsUQ
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
FIA App K Historic Racing Imp - Bevan Tribute - www.shag.no
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