Engine Down on Power (Or is it?)
Turbo Mini Forums

Hi,

I'm a bit dissapointed to be honest, my engine is really down on power from what I think it should be and am wondering what the main cause could be. It was rolling roaded at slark engineering and its running a megajolt. I really want more power, looking at other engines of similar specs I should be looking at maybe 90bhp at the wheels, I currently have 60bhp at the wheels.

I am running a stage 1 kit from minispares which had a 3 into 1 exhaust manifold, this really needs to be a 3 into 2 into 1 i think, am i right in saying this, and just how much could this be restricting the engine??

Why is it so down on power and what can i do to sort it out?

Its a 1330cc.
It is an a+ block bored and honed +60 with omega piston.
Kent 296 scatter cam.
New followers.
New oil pump.
New big ends, mains and thrust washers.
Centre oil pickup.
Lightened duplex chain kit.
The block was decked 10 thou.
The head is a big valved mg metro 12g940 which has been polished and ported.
The head has had 30 thou skimmed off it and the valves were all re seated.
It has double valve springs.
This Engine is sitting on an a+ metro gearbox.
Its on a 3.647:1 diff ratio

Thanks

Jon

Compression ratio is what??
Carb/s are what??

Also as you say a proper LCB will help matters.

Hi,

Sorry, forgot the carb, its running a Hif44, also when you say compressions ratio, is this the one I did for each cylinder? Not too familiar with the terminology?

From memory they were about 180 across all four but will double check the figures tomorrow, i have them written down at home.

Would a proper LCB give a decent increase, as im sure the one i have is restircting the engine.

Would i be better off spending more and getting a full race one with 3 seperate pipes?

Thanks

Jon

i think the manifold and head will be your limiting factors personally.

teh head would unleash more power than the manifold though.

Edited by Nick on 4th Jun, 2009.

what size wheels you running? you could drop 10% power if your on 13x7

133.5 bhp 123 lb torque 116mph @6640rpm 9.5psi
Shakespear RWYB 14.995 91.83mph

Compression ratio is the compression ratio, e.g. swept vol plus unswept vol divided by unswept vol. I'd guess it would want to be 10.5:1 or more to work with that cam.

This spec should produce more power really.
What have you timed the cam in at and who did the head? The manifold is prob a bit restrictive, but wouldnt be losing you that many donkeys.

90 bannanas would be what a very good one would make at the wheels, and is much dependent on the head.

Edited by retroracer1380 on 5th Jun, 2009.

I agree with the above.

1. Who did your head
2. What is your compression ratio?
3. Where did you time your cam in?

When you say 3 into 2 into one, do you mean a LCB?

A 296 really needs high compression and a free flowing exhaust.
And, you'll never see 90 at the wheels with this spec and a Hif44.

I just had a very similar engine on the rollers. it produced 93 at the crank.

IMHO the most that spec will make at the wheels will be 70 which is + or- 90 at the flywheel. What RPM did it make your current figure at

Hi,

Thanks for all the replies guys its really helpful.

The compressions are 175, 170, 185 and 190.

I am trying to find out the compression ratio from the guy I bought it off as a complete unit so the engine i bought is as he set it up you see.

The bhp was 76.3 hp at 6098 rpm, at 94 mph, to give you an idea.

Things to be done:
Head work
LCB Manifold
Timing gear and check cam timing
Possibly new carb, my thoughts on this are bike carb??

Thanks again for the advice

Jon

I would be inclined to fit a 3 into 1 manifold with a 296 scatter cam. Everything is at the top end and that is where the 3 into 1 is best suited


When Tom is talking about compresion ratio, he is talking about the physical ratio of swept volume against swept plus unswept volume, not compression test pressures, that is a completely different thing. I suggest you read up about compression ratio, as with racey cams you need to get it up to something resembling 11:1 and above

Dont wast your time on bike carbs, fit twin SU HS4s or a Weber

you have quite a veriety with the compression ratios you should try and get them all pritty much the same, i thought the turbo boys were runnning about 170ish psi possible headgasket failer?

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

I got 112bhp out of my 1330. Basically the same spec as yours except I had a minispeed stage 3 head. I was running a hif44 with no problems. What fuel pump are you running??? Is it up to the job?

I am running the standard mechanical fuel pump.

Jon

this wont help really, get a red top pump on there! search for compression and have a read! Then speak to one of the lads about getting your head done

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

If the engine doesn't run lean at any time, I guess the fuel pump is OK.

You will still be ok with a mechanical pump at this spec i used to run one at 85horse on an old 1380 with 286 and no probs.

As previously said you need to be about 11:1 compression ratio with a cam like that.

I wouldnt worry changing carbs, a hif44 is perfectly up to the job. I still run one on another 1380 with 649 cam and its producing 90 at wheels. Bear in mind power figures differ from one rolling road to another