supercharged 1275 home brew. anybody fancy a blown minor?

Post by **superchargedfool** » Fri Aug 01, 2008 12:13 am

sod it.

mojo rteurned.

I am going to build a proper bottom end so as to run 10psi!

Should be around 140 bhp.

power to weight ratio of about 200bhp/ton, or put another way plenty of acceleration and top end.

My theory is that I am not going to build an engine suitable for the supercharger but I am going to build a typical track day engine and then fit a decompression plate.

It seems to work for the mini boys!

I am thinking +20 1293cc, full rebuild, new standard cam and oil pump, balanced, forged pistons, wire ringed block so a group a head gasket can be used. maestro head posted and polished and 1.5 roller rockers, 45 dcoe and a modded dizzy to limit advance. Oh and supercharger for good luck!

Sometimes you just have to realise that biting the bullet is the only way for a man to go.

Should be possible for a grand. Just won't tell the wife.

I love the car to bits as it is with reasonable results but I am now just starting to think that maybe I could possibly build and own the quickest a series road legal minor, and a sleeper at that.

Watch this space for engine build to come shorthly.

I know I thought about a bike engine but I feel it would loose the ethic of the car. I think you know what I mean.

I am impressed by quick minors but more so if they have an a series rattling away under the bonnet.

Post by **aussiemike** » Fri Aug 01, 2008 5:58 pm

cool that sounds lie an ideal plan!!! do you know if your supercharger has a 'flow' limit? i.e if it runs out of steam on engines trying for 200hp? just wondering how you size a blower for an engine is all.
cheer,s michael.

Post by **superchargedfool** » Wed Aug 20, 2008 11:38 am

hi all, been a while.

I have just paid for a set of new pistons!

omega have just made a few sets of dished forged pistons. I got the second to last set. I think one more set is available, but not for long.

They are +20 18cc dished forged jobbies.

They were not cheap but will be able to take a fair bit of abuse. Watch this space because a 10psi charged minor is coming here soon.

Should be fun, will be at least 130bhp with serious torque.

charger will be well up to it as new mini can run up to 200bhp on standard charger.

Post by **aussiemike** » Wed Aug 20, 2008 12:34 pm

excellent! keep us up to date with build pics etc.
cheers,michael.

Post by **bmcecosse** » Wed Aug 20, 2008 3:02 pm

Not much point using a 45 DCOE into a Supercharger - far far simpler to just use a nice big (2"?) SU. You should seriously consider water injection if using that kind of boost.

Post by **minor_hickup** » Wed Aug 20, 2008 7:23 pm

Or an intercooler?

Post by **bmcecosse** » Wed Aug 20, 2008 9:58 pm

Yes - but supercharging doesn't add as much heat as turbocharging (no heat transfer) - but there is still the compression heat increase since P1V1/T1 = P2V2/T2 !! So - it may be worth while although there are flow losses and throttle response issues to cloud the decision.

Post by **superchargedfool** » Thu Aug 21, 2008 9:34 am

there are some very quick mini's running 140 ish bhp with supercharger and no charge cooling.

Post by **superchargedfool** » Tue Oct 21, 2008 3:41 pm

Well, I have recently bougt off ebay a marina that even came with a spare 1275 engine. So I now have a spare block to send to the engine builder.

Now that I have the spare engines in the bag I thought I would up the boost again.

We have fitted a larger pulley to the crank. It blew the engine up the last time it was on! I have fitted a spacer plate between the head and block and plumbed in a bypass valve between the inlet manifold and the supercharger entrance.

So I can now by means of a 15mm plumbing gate valve moderate the boost a bit.

The first run with the valve fully open gave 10 psi at 5k rpm. Oh my god did it go.

As the engine warmed up and the piston crowns got hotter, detonation started so I disconnected the advance as a temporary measure. This stopped detonation except at very high revs.

Even with the advance disconnected it went like stink. I would say that acceleration in 3rd was a bit like a standard cossy. And I am not kidding.

I am now looking for a slightly smaller pulley to make fit and aim for about 8psi because I think it will be ok with the very low compression ratio. Its just under 8:1 at the moment.

I can't wait to get the stronger bottom end built and in so as to run these sought of boost figures safely.

My mojo is definitely back for this car at the mo.

Post by **d_harris** » Tue Oct 21, 2008 9:22 pm

Good Stuff!

Post by **superchargedfool** » Wed Nov 05, 2008 11:27 pm

well, I have done a few miles over the last few days with 10psi at full chat and my god it feels good.

I have done a standing to 60 on a gps in the mid 7's and it feels amaizing. Fueling is with a bbc needle and it isn't rich enough after 4k. So will need a bit of filing.

The acceleration is mind blowing for a moggy. It goes like an RS Turbo. I have a huge smile on my face every time I drive it, but keep waiitng for the horrible sound of it dropping of a cylinder, but so far so good.

Thank god I have the spare block in the wings for the rebuild for when it all goes horribly wrong!!!!!!!!

Post by **philsheredan** » Sun Nov 09, 2008 5:57 pm

Hello supercharged

I just read all your posts and I'm glad you didn't sell it as you and I both know there aint many cars out there with the same grin factor. Its a shame were not closer we could have had tested our boosted beasts.

mine just got its mot and therefore free roadtax and is almost ready to be my daily car again.

I'm runnin a standard midget bottom end with gearbox,hydraulic clutch and metro turbo top end, high pressure fuel pump and boost sensing fuel pressure regulator, standard dizzy with electronic ignition and no advance, adjustable boost control and the grin factor is awesome all i need now is a 3.7 to 1 diff to stop it runnin out of revs too quickly !!

she still looks like an old breaker which adds even greater grin factor when the drivers of sportier cars get left standing at the lights.

Dont sell it !

Phil<br>

<br>

Post by **superchargedfool** » Mon Nov 10, 2008 9:04 am

sweet to see another boostedfool.

I love my car whilst also hating it. But oh my is it fun. And yes it is fun to see the faces of boy racers when you catch them by surprise.

Post by **superchargedfool** » Mon Nov 10, 2008 3:27 pm

well I am well and truly in a good mood.

I have just pulled the engine out of my ital donor and taken the head off to measure the bore size, hoping it wasn't rebored at all or +20 at max, and it appears to be standard at 70.6mm.

I bought the car for the engine that was in it and the one that came with it hoping to find one that was usable at +20. The spare turned out to be much overbored so was useless to me, but the one in it has made my day.

The serious engine build can now begin............

Post by **bmcecosse** » Mon Nov 10, 2008 4:50 pm

What's wrong with having the overbore ?

Post by **superchargedfool** » Mon Nov 10, 2008 4:58 pm

general consesus of opinion in forced induction a series circles is that +20 is the max before the gap between cylinders becomes narrow enough to lead to head gasket issues.

1400 has been done with boost but as far as most people I know are concerned +20 is the safe limit for boost and an a series for the head gasket.

Post by **superchargedfool** » Fri Mar 27, 2009 1:43 pm

well donor engine has just gone off to the engine builder who is going to be doing it.

He has the bottom end which is going top receive the full treatment and he has my minispares £440 head that I got for nothing to make sure that we get the right comp ratio.

We are deffo going for 140 plus bhp.

Looking at an intercooler, ren 5 turbo carb rather than suck through. Its going to get all serious!

I am so so excited at the thought of even more power than it already has.

If I wanted to run moderate boost we would have comp ratio of 9:1 or just under but we are looking to be nearer 8:1 for 10 to maybe 12psi. Who knows it might be quick?

Post by **superchargedfool** » Wed May 06, 2009 4:11 pm

engine is now ready to go in so will start pulling moggy to bits in the next few days.

MOT today with no real problems.

BUT, yuk. I have spent the last few hours brushing and scraping and then waxoyling the whole underside and up the arches. Lovely when done but horrible to do.

So this week new MOT, new engine, new tax, waxoyled and have hardly driven it at all.

Post by **superchargedfool** » Tue May 26, 2009 5:07 pm

YES.

New engine is in and running.

Sounds too sweet and quiet for my liking.

Can't rev it up or abuse it and it is going to kill me running it in.

Will get it on the dyno early next week and hopefully report some smug bragging figures.

I am so excited at the prospect of 140ish bhp in a light minor, I feel like an expectant kid just before xmas waiting to open his pressies.

As a side note have made a panhard rod and mounts from bits and bobs that were cluttering up the place. Will post photos of it on it next few days.

Post by **aussiemike** » Tue May 26, 2009 8:15 pm

photos!!!!!!!!!!!!!!!!!!!!!!!!! really glad you have gotten back into this project as it was too good a thing to sell off.
cheers, michael.