highest boost for 8,6:1?
Turbo Mini Forums

I run 8,6:1 CR on my turbo mini.
What could the highest boost be (but still safe for every day use) with intercooler or without it?
Gregor

There is so much that can change this but i would guess at around 14 psi?? probably run more but that will be very safe with a intercooler and about 10 psi with out.

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

Just out of interest, what compression ratios do people run and where is your boost threshold abd max psi?

I run 7.3:1, 20psi and the boost threshold is around 4000rpm.

Its only 998cc though.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Hell mate 20 PSI on a 998cc that must be good fun, have you any power figures as it would be good to know what that's making. And as for the C/R i did realise you could get a mini that low!

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

My 1380 with standard deck height and a standard head came in at around 6.2:1, had the block decked ~3mm and the head skimmed 2mm to bring that back up though :)

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Isn't that an unswept volume of 66cc?

A standard head is 21.4cc, pistons 11cc (max), head gasket 4cc. That's 36.4cc total. where's the other 30ish cc? I've just done this off the top of my head so I could be massivley wrong.

I feel like I've mentioned my power figures lot but its 120bhp, 120ft lb torque.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Ok i've just done the sums on the 6.2:1 1380 motor and you would have to have a head volume of 37.13cc.
Now if you decked the block to 0cc and kept the head volume std at 21.4cc this would give you 10.1:1 comp on a 1380cc motor.

Bore 73.5mm
Stroke 81.4mm
Head volume 21.43cc
Gasket Volume 3.9cc
Ringland Volume 1.6cc
Piston Dish 11cc
Deck Volume 0cc
All This = 10.1:1 Compression Ratio.

6.2:1 i very much doubt unless the piston was around 6.75mm down the bore giving a deck volume of 28.63cc.

Karl.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

Yes guys that does sound a little to low , as my 1380cc pistons came close to the deck high, and only tho was skimmed off the top of the deck and head.

any way, that's good torque you have there on that we engine! for the CCs. well done:)

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

pistons were 6.something mill down the bore and dish of 16cc. They wernt origionally for the a-series as far as i can tell. had a little hunt for my origional calculations, but cant find them anywhere :(

Accralite have them on file, but didnt tell me what engine they were designed for, just that there intended for a 73.5mm bore. assume they were done at customer request. Anyways, there in the car, they work, and theyre shiny and thats all that matters :)

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

The latter is very true if they fit and work thats all that counts...

I'm now going hunting for more info on these pistons as i've used triumph pistons in the past at 74mm that worked great.

Karl...

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

the triumph pistons arnt quite 74mm, more like 73.7mm, iv got a set of em too (if its the same ones ur referring too) came out a short block 1430 i purchased a while back. horrible pistons, got that nasty big slotted oil groove and a really long skirt. IMHO ofcouce!

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Triumph pistons are 73,65 mm.

There are several engines with "suitable pistons", 72-73 mm variants in several Toyotas and Nissans, late model Opel Corsa (Nova) has a interesting one, as well as Skoda with flat top. Most of these require either small end bush or piston pin bore machined to Mini size.

Strength is an issue that remains...

AS for basic layout, I would keep the piston close to deck (at TDC piston within 0,5 mm distance from the block deck, preferably flush) and play with piston dish/chamber volume. Burn characteristics, tendency to pink etc depends on relative position of piston vs. chamber and if the piston is several mm down in the bore at TDC you will not have an optimum performance. There?s a lot of discussion of squish area (the distance between piston outer rim around dish and head surface) and most pro engine builders quote figures between 0,7 - 1 mm. As funny as it sounds, with tight squish you can have more ignition advance and still the engine does not detonate. Bigger squish distance will lead earlier to detonation, and only way to deal with it is to retard the ignition, and in the end lose some performance.

Another issue is the thermal loads that the top of the cylinder is subjected to. I would keep the burning in the head, not down the bore. Again, just a personal way of building engines...

Jukka

Yo Jukka are you states side ??

If so have you ever had a price from J&E for pistons.

Karl.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

Pretty sure he's Netherlands...

check you him home page (link in the links section)

alex

AlexF

Nope,

just the opposite direction; Finland.

No, never enquired JE pistons. My mate has ordered a set of pistons for trick Mini Seven racer. I?ll ask which company he bought from. He did ask several companies in USA but some did not even bother to reply.

I am running 73,5 mm Omegas and have a new set of Omegas as a back up. You know, if you have a spare set they never break... that?s why I have a set of driveshaft in the car.

Sorry Jukka!

Least I was vaugly in the right direct, even if I missed by a few hundred miles!


alex

AlexF

Afraid i have no idea what engine these particular pistons were for, only that they were intended for a triumph engine, found some triumph forum a while back and posted the details.

But there definately not intended for a bore that big, the block these came out of was bored to under 74mm.

AE 18463 if its of interest.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

jukka, jstu a quick note re-haveing pistons so far down the bore!
Asume it was aimed at me :) Cheers for the info, tis my 1st engien build and learning all the time, il run this one til it blows up and learn from my mistakes :cool:

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

good plan evo :)

If everyone does this and share the result on here, we might finally have a decent knowledge base on our engines :)

alex

AlexF

73,65 mm pistons were used in Spitfires and 1300 sedans (Toledo ???) One of them had split skirt, the other not. Either of them are more or less outdated designs and in my opinion not worth the hassle. There are stronger (but expensive) modern pistons available that need no tricks to fit. If you want a cheap big pistons for Mini engine you can use 1300 Ford push rod engine piston. 74 mm, correct comp height plus piston pin is of same OD as Mini. Naturally it is a flat top piston and totally out of question in turbo engines (sky high CR)

My ideas were only advice based on what I have tried/read or vice versa. Not directed to any specific person. I am from old school (well at 38 years not THAT old), I usually think the engine combination through, try to figure out different ideas etc. I also believe that it is wise to spent some extra money for good pistons, build the bottom end right and then update the top end if necessary. E.g. having the pistons flush at the deck means that you don?t have to get something ultra trick head to replace a worn or outdated head.

Also, fitting something like Carrillo, Arrows or whatever rods in a street engine however powerful is total waste of money. Same with cranks: factory cranks have proven to take just about any abuse. Point being that turbo engines seldom need to rev higher than 6500-7000 rpm. If high revs are used all the time then things get different...

But basically that is what these forums are for: questions and answers and advice. I?ve done a lot of reading: my library of car magazines exceeds 1000 magazines spread over 25 years. I have saved all worth keeping. I read a lot of US magazines like Hotrod, Popular Hot Rodding, etc. Sure they deal with V8 engines but basic engine building is applicable to any engines and there are always some nice ideas to try out.

first of all 38 is YOUNG !!!
i have read a lot of things you have posted on many mini notice boards and respect everything you say , because you have done what you are talking about!!
What pee`s a some of us off is the advice "freely handed out by so called experts" when all it is something they have heard, been told or read in Max Power.
There is no real secert in running a high boost turbo , but so many people get it oh so wrong.

Everyone knows that instructions only have to be read if the thing doesn't work....