bmw 16v build help.
Turbo Mini Forums

Hi.

my 998 idea was very short lived (thanx for clearing that up)

the stuff i have on the shelf;

16v K1100Lt head w throttle bodies.
unbored 1275 block
set new p21253 pistons +60

I more worried about getting the engine to stay in one piece when revved to BMW levels to get some truely GTI killer power (which means >8K). I am NOT looking for Jimster power levels but 130 to 150 bhp at < 7K rpm would be the goal. it needs to last and not guzzle fuel at silly rates

thus some form of force feeding seems in order.
and as you need a manifold made anyway.

the plan so far:

low boost,relatively high CR,properly intercooled to help with detonation supression. mains oil gallery mounted piston sprayers
lehman style double chamber plenum with single TB for simplicity. i guess flywheel mountedturbo. injection of course.

i have a load of unkowns that i could used some help with.

I only want low boost up to 8 psi-isch. what kind of turbo unit would suitable T2? will the 21253 pistons be useable or do i need something sturdier?


any tips very welcome !

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

if i was only looking for 8 psi boost i'd seriously think about using a charger,

eatons from BMW minis are still not lots of money, plus you save all the aggro of the exhaust system and gain a bit of response.

i have spotted eaton chargers for decent money

but the downside is that they are rather large and are quite inflexible with regards to mounting..

but i will see if i can dream up a manifold when i keep the blower low and in front of the block.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

TBH the power your after should easily be achievable in an N/A setup. I think JohnK has 163bhp on his! And it should be good on fuel too compared to a turbo.

Im no expert on pistons, but you have to be careful on selection because a fair chunk needs to be machined away for the valve reliefs.

Running +60's with a 12cc dish (as far as I remember) in those pistons means you'd have a seriously high CR as the head chambers are only 18cc's.

If wanting to use the parts you've already got I would think a turbo setup would be out of the question purely because of the CR's you'd be running? Stand to be corrected though!

Edited by matty on 11th Sep, 2007.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

the k1200 s gets about 130 bhp from 1171cc at 8750 rpm with a cr of 11.5..
that is a with a slightly hotter cam.
so a 1330 should make around 140 bhp..but still at >>8K rpm. i would like the same power but at around 6500 max

the pistons are not a given and as said on the shelf. the build a bottom end with will reliably cope with 8500 rpm requires a fair bit of upscale bits


the pent roof is as far as i have gathered quite detonation resistent and using intercooling and 98 octane fuel I would suspect you could be able keep a fairly high CR...

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

If your after the goods low down then the turbo is the way to go, Im not a fan of the supercharger.

You are right that staying below the 6500 (though i would stretch it to 7000) wont need anything other than a hardened standard crank and standard rods. Id personaly get the crank cross drilled, that way you could take it to 7000 on ocasions. Im sure Jimster is looking at his dyno print out, at where the power is still on the up at 6500/ 7000rpm.

The pistons as Matty said, is the issue. Its difficult enough to get the compression down as it is and to get it to a decent level for boost, you are looking at a mega dish in the pistons and or a thick head gasket. The 21253 pistons, well thats your choice, some people have good power on these and they survive, but they are a budget piston.

Dont forget that the head will need skimming once the welding has been done, again it depends how much is taken off.

I achieved 9.4:cr with standard size pistons machined out to 16cc, 0.5cc ring land clearance, no piston to deck volume,3.2cc gasket volume and 18cc chamber volume. Thats on standard bore, You would have to acount for the extraca with +60thou and 16cc is already big in piston terms, the 18cc turbo pistons looking like a good option, Accrilites posibly?

The other thing to consider is the cams you are using. The LT cams should be a good choice for boost, RS cams are a little racey.

Surely the old LT on the intake and the RS on the exhaust would make for the best boost setup. With minimum overlap. ?

Bugger off, I'm getting there.

i know this is kinda missing the point, but if you don't want a really revvy engine, and you're only after 130-150bhp, surely a 5 port turbo would deliver the goods.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

but it would not look as pretty..

I know i can get about 115-120 bananas from a resonable NA 5 port. that is even more simple.

a 16v 1360 will probably get about 125 bananas at 7.5K rpm

maybe i should rephrase to mostly low boost 5 to 8 psi.

but even 5 psi boost ( with adequate air mass) on a well designed manifold on the BMW head should give roughly 25% increase..i.e. 150 isch BHP.

if I need new pistons i might just as well go to a +20 with a big dish like the acrralite ( thanx for that head up) that way the CR can be kept down to sensible levels (but not really low either).

it is an engineering/learning exercise as well.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

With 18cc pistons, the thickest gasket SC do and standard 16V chambers you should be around the 8.95:1 area.

I am assuming that you will be using injection thus an ECU, which probably would have some knock detection / correction, which means you can run a lot of boost into the motor.

My 4AGE (toyota's BDA) engine I had in the kit ran 12 psi on top of 10:1 CR with out a hitch and very very rarely did the ECU sense knock, basically only when the IC was allowed to heat soak and the inlet temps had risen by quite a bit!!!

If your only planning on running moderate boost with management I'd not drop the CR much at all. After all the higher the CR the better the engine off boost, faster the spool and bigger the grin!!!!!

Every day is a school day ...........

How fast and how expensive ...... the same question...

Roger, have you added the value for for the valve pockets when working out your CR?

You can get it quite a bit lower than 8.9:1 for a 1293!

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

Matty, your right ... nothing taken into consideration for the valve pockets and my calcs are always based around a 73.5mm piston.

You really don't need to go below 9:1 anyway as the cooling in the head (thus combustion chamber) is much better than the A series, the pent roof a little more det' resistant and you'll be on proper management (rather than a bucket with a hole for fuel and an old clock spring doing the timing!!!!). Add to that the fact the ECU will be able to hold maximum "safe" settings on a feeback loop and robert's your mother's brother.

Every day is a school day ...........

How fast and how expensive ...... the same question...

thanx fo the thoughts ya'll

definitely injected

Does knock sensing work on a three main bearing relic like the a series?


I seem to remember that Endyn use a CR of around 11 on supercharged honda engines at silly boost ..on US grade pump gas.

I'd reckon it makes more sense in using a higher CR and a big intercooler ( and 98 octane petrol) and use water injection for short forays into high boost

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

ask these?


pole star aparently do knock sensing...

http://www.lynxaelr1.co.uk/Products-Mini.htm

also, with the lack of A series valve gear there will be less nose to be picked up.

and I think knock sensors are usually tuned/filtered to a particular engine, the knock frequency is related to bore size IIRC.

Edited by Joe C on 13th Sep, 2007.

I have yet to try and set up the knock detection on my engine. I was however told that with background noise of the straight cut gears, it could proove difficult.

Knock occurs at a fairly specific frequency 6400hz or something so is distinct from all other noise, it all depends how good the filtering of the knock signal actualy is as to whether it will work or not.

Knock should only be used as a safety rather than an active control. The ignition should be set up and checked properly on the dyno so that it doest knock.

I agree with Sprocket ... knock is only there to save an engine.

I should have been more specific, I meant to say optimised AFR, boost reduction with increased inlet temp, properly timed sequential injection etc.

Edited by RogerM on 13th Sep, 2007.

Every day is a school day ...........

How fast and how expensive ...... the same question...