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engine performance options
https://www.ausmini.com/forums/viewtopic.php?f=2&t=74326		 Page 1 of 1
Author:  wolfmini [ Fri Nov 25, 2011 7:12 pm ]
Post subject:  engine performance options
Hi i have a 1275 cooper s motor, with a unknown cam (but sounds lumpy)
it also has a 123 ignition
as a rough guide it produced 64 hpatw
i was going to see if i can get a bit more out of the engine
what are my best options
* sending the head to graham russell for porting etc. (do i really need to know what cam i have before doing this?)
* putting in 1.5 rockers (on the sales websites it says can give the same performance as a high lift cam, but will these work with my unknown cam?)
i'm trying to avoid rebuilding the engine and if possible removing the engine
im open to any other ideas, and what performance gains i could expect
Author:  wolfmini [ Fri Nov 25, 2011 7:41 pm ]
Post subject: 
just been reading some old posts, looks like i should stay with 1.3 for road use
still im not sure if i should pull the cam out and get GR to regrind it when i get the head done
i would like to get an extra 30hp or so
Author:  74snail [ Fri Nov 25, 2011 8:00 pm ]
Post subject: 
If want a massive increase in HP and you have the budget then move straight away to a Honda or BMW head and turbo charge it , straight cut drop gears , straight cut gears , 3:9.1 diff

Matt Read is closer to you so if you have the budget PM him so he can steer you in the right direction for a Turbo Twinky conversion , he's on the mend at the moment but he likes the smell of moolah and I,m sure he,d be happy to help

http://www.ausmini.com/forums/profile.p ... file&u=451

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Author:  wolfmini [ Fri Nov 25, 2011 8:20 pm ]
Post subject: 
im trying to keep this mini a bit more stock looking, so bimmer conversion is out for me
Author:  74snail [ Fri Nov 25, 2011 8:29 pm ]
Post subject: 
wolfmini wrote:
im trying to keep this mini a bit more stock looking, so bimmer conversion is out for me


To get your specified 90HP is going to mean $$$ whichever method you use to get there , a full engine rebuild to make a strong motor that puts out more than 80HP will cost more than $5,000 , you can,t cut corners if you want more than 80HP

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Author:  Lillee [ Fri Nov 25, 2011 10:36 pm ]
Post subject: 
Whichever way you look at it, bolt on mods to get to you near 100bhp is going to be difficult ($$$) without forced induction or some other $$$$ bolt on mod.

A well ported head is worth 30bhp for sure (I'd argue more), but with conditions: Compression ratio (that means piston dish and type), cam profile, bore size, carb, exhaust and most importantly tuning. There are a lot of variables and depending on how your current motor has been built it, you may only realise some of the benefits before running into other problems like fuel starvation, oil starvation, diff issues, gearbox issues, etc etc. Brake issues, drive line issues, tyres, the list goes on.

It basically starts to bring out your car's weakest points. Example: If you have an unmodified crank/rods/flywheel setup and it has not been balanced/lightened then you will feel that the 100bhp that you have is not the same as an engine that has had this treatment, for example.

This is one reason why I decided to just buy another 1275 and rebuild that from the ground up. The cost will be similar either way, but at least you know what you put into it and how it was built. (HINT there is an Auto 1275 for sale right now in For Sale section for $250, from someone in QLD I think, bargain :P )

Example: my engine now has a few problems, not major but they are there such as noisy lifter, gearbox problems etc. Suddenly a Quaife LSD doesn't sound too far off, and my Yoko A008's just don't cut it anymore. This is what happens when you are running 100+ bhp! it's not a simple matter of bolt on and go, it's a fine tune to get it to the edge and a fine tune to keep it there.

100bhp is not one silver bullet, it is multiple pieces as part of a whole package... if you get my drift...

Hope that is some food for thought... :wink: :wink:
Author:  willy [ Sat Nov 26, 2011 12:47 am ]
Post subject: 
And a 100hp (at the wheels) engine isn't the nicest thing to just take to the shops.
It becomes a chore! :twisted:
Author:  drmini in aust [ Sat Nov 26, 2011 10:47 am ]
Post subject: 
Getting 100HP ATW from a N/A roadgoing Mini is a pretty big ask, IMO. Unless you want a street bound race car (ie. a cop magnet).
As an example a few years ago at the 1st ausmini Sydney dyno day, we had a dude rock up from Melbourne in a $40K+ custom Mini with a fresh $13K engine in it, built by Link Automotive.
1430cc, Weber, a big cam, head & rockers, race manifold yada yada it made about 82HP ATW. This was the top NA figure for the day. Most of the quick road Minis (mine included) on thid day made around 70-75HP ATW.
The dyno was a Dyno Dynamics one running in shootout mode, sure all chassis dynos are open to fiddles but these are more consistent than some.
If you really want to know what the real HP is, put the motor on an engine dyno. These are calibrated accurately.
Author:  wolfmini [ Sat Nov 26, 2011 2:14 pm ]
Post subject: 
thanks for the replies guys, i might do some head work and put in 1.3 roller tip rockers and leave it at that.
question before i send my head off to gr or matt what specs do they need to know?
engine displacement? does this need to be percise? to get the correct cr?
cam?
anything else?
Author:  74snail [ Sat Nov 26, 2011 2:44 pm ]
Post subject: 
The information for a head modification to work out the compression ratio needed is the bore size and the the degrees that the inlet valve closes, if you use flat top pistons them the head will just need to be refaced , if you use standard pistons then you may need to go down to a chamber of 20cc

The 12G940 head I got from David Rosenthal had about .045" off it to give me about 9:6.1 compression with standard pistons, the chambers are 19.8cc , David said in my communication with him to get the head sorted

" Most people take the stroke as the base for compression ratio but I work from the inlet v/v closing. with a N.A engine the air pressure in the cylinder at that point is still well below 1 atmos.
Although most go by the actual ratio the other critical factor is compression in the cylinder at the instant of ignition. If the pressure is above 190psi then pre-igniton can occur under load. Too low ie 140 then the engine is very sluggish. I try to get it around 170-180 so a engine with reasonable air flow would end up with a compression ratio of around 10:1. "

over to you

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