We always love these questions. The most documented A15 HP I've seen is 156 at the wheels, this is with 14-1 compression, 300 degree cam etc. this motor as Dave said will go all of 6 hours. A12 will be 100 at the wheels. These are non turbo figures.
The other thing people always forget is the motor won't pull much below 5000 RPMs, so you'll need some for of close ratio gearbox...............as always what do you want out of the car?

Tom

Hey DD: I am not mechanically minded but I dont think 25,000 klm / $5k / 120/A15 at the wheels sounds right. Slightly off topic,Ive spent just under $7k for a S/c A14 to get a modest 120bhp cause thats all I wanted with the intention of 120 bhp with reliability and long life. Yes if I thrash the ass out of it,like any motor, it will definetly shorten the life, but with a spurt here n there, I'd be pissed off if I only got 25,000 klms out of it. Ok I know this topic is for N/A motors but I would honestly expect double the life atleast. And just to prove a point, I wanted 140 bhp at the start with h-beams and forgies then decided to drop the hp and removed the H beams and forgies, cause I was told the it was not necessary and keep em for another project. I am running stock pistons and just stock peened rods. If were talking A15 N/A with 150 bhp , I'd agree with Rallytwit and expect to get around the block once for $5k cause rev's kills motors and also what application is was build for. As a streeter I'd expect a longer life for my buck

this engine builder in sydney mentioned it when i was going around for quotes, its a daily driver but i have done a few track days in it, soo reliable and hi performance engine ? what would i need to do to achieve this? what would turbo or supercharged figures be like?

Maddatter, have you asked Bige ?? Im confident he will give you an honest bang for ya buck !!

which engine builder told you 225hp out of a12 n/a. sorry but, i find this hard to believe they would say that.just curious, if he guarantees that hp, go with them. how much was that quote. then what happens when it doesn;t make that hp.( thats 3hp per cubic inch on n/a) big call.(2hp per cubie is very hard to get)

Maddater, how much were you quoted for 225 hp motor ??

im looking for more performance, he didn't exactly guarantee anything, he said 225hp , im juat saying what he told me , i have been to around 6 places and there all ranging $5000 too $9500 roughly for half decent performance, i want something that wont die on me after 6 hours and is strong around the track

pm sent. if your interested in a engine build contact me.i've built quite a few for other members etc,cheers

Bige, didn't you recently have a built A15 on here for sale in the $5K range w/no takers......what was that motor, perhaps that'll give the OP an idea.

I've no idea what my HP rating is but I've got about $1500 - $1800 US into my A15 - Weber DCOE w/Cannon intake, mild street cam, ceramic coated header, dual springs, .030 over block, H72 oval port head, new guides, I did not port match the head (should of...) thats just the motor too. I had the rad re-cored & an electric fan, new heater core, etc...

my .02 cents......

225hp from an a12 NON turbo? that'd be something. During their peak in the late 90s (which is some time back but outputs haven't risen astronomically since then) 2 litre supertourers were making in the neighbourhood of 300bhp . That's 150bhp per litre, from a 4 valve race engine that would have been rebuilt after each and every race weekend.Those cars were costing the teams close to 1 million dollars (perhaps 1.3 million in today's money) to build, and the category underwent massive rule changes to keep it alive as it was simply costing so much that not too many teams could mount a competitive challenge. That's 200bhp per litre with a 'practically' unlimited budget using pseudo production based engine blocks - 4 valves, and huge development.

To get 225 from an a12 (even assuming it is out to say 1.3 litres) - that's around 170bhp per litre, from a 2 valve production based head/block combo. hmm.

We could even look at it semi mathematically. this won't be dead accurate, but it's a handy enough tool. normally aspirated engines make torque outputs which very closely match volumetric efficiency (friction, and combustion efficiency play a role, as do other things, but it's remarkably close to engine size and volumetric efficiency). what this means is that if we got 100% volumetric efficiency on a 3 litre 'race engine' and on a street engine of 3 litres - at that point both would make around identical amounts of torque. Where the extra power comes in (once you have actually gotten up to maximum volumetic efficiency - or maximum cylinder filling, which can go up to 130-140% for the most highly developed custom built race engines (and unlikely any a series) - well power is a product of torque AND rpm. So if you can make the same torque at double the rpm, you have double the power. Interestingly enough, formula 1 engines don't actually make astronomical torque per litre. It's the fact they are spinning up to 2-3 times as many rpm and making that sort of toque up that high that they produce such phenominal power. it's also worth noting that peak torque will drop off and you might be a good 5-10% down on peak volumetric efficiency (ballpark) at the rpm where you make peak hp

Ok, so let's be generous and say that we could hypothetically get an engine to hang on to peak volumetric efficiency at higher rpms than normal. let's also be generous and say that a well developed a12 based motor could make around 120 ft lbs of torque and maintain it as far as you need to make that big power figure. Well if it was making 130 ft lbs at 10,000rpm it would be making 228 flywheel bhp. Or about what that guy claimed he could deliver. If we go a little further and assume (quite rightly) that ve and torque will in fact taper off and start to decrease by such high rpm, we could more likely claim about 110 ft lbs of torque (and that's still DAMN generous at such high rpms) then to make 225bhp it would have to be spun up to 10,700rpm . Remembering too that typically to get full use out of an engine's powerband, you tend to rev the thing perhaps 5% above peak hp rpms before upshifting (and it also depends on gearbox ratios as sometimes you have to rev it higher to avoid it being yanked down and below the engine's powerband on the upshift)

That's just not realistic at all. even if you could port the head to provide the flow numbers, cam and valvespring life would be measured in minutes (I don't mean it'll blow up in 1 minute, I do mean it won't last 'hours and hours' - maybe a race meet, maybe a drag race weekend, not an endurance race) so would connecting rods and pistons. Heck, at that rpm level, even with the a12 having a more rpm friendly shorter stroke, you'd start to worry about teh block itself failing sooner or later.

If I recall correctly - BigE had some methanol fuelled speedway engines - a15 based - I think they were making just shy of 200bhp. With more capacity, and the fuel that makes the most power (short of using nitromethane or similar, which is a sort of 'chemical supercharging' since it releases oxygen to allow more fuel to be burned, a bit like nitrous oxide) out of practical fuels you or I could access.

One thing I learned (eventually) started when I was in my mid teens and still an apprentice. I was turbocharging holden motors (or trying to) and pursuing all info/knowledge I could. There were a number of turbo performance type vendors and workshops and I'd go there and bug them (time permitting) whenever I had a spare minute or two. you just wouldn't believe some of the BS power figures some quoted. I didn't know they were BS at the time, but I obviously learned (the hard way) that engines are anything BUT indestructible.

Around the same time, there was one bloke, who sang a different tune, so to speak. When asked about compression ratio and safe boost levels, the figures he quote were well below what the other blokes claimed. It didn't sink in at first and I was inclined to keep asking other people questions until they told me what I wanted to hear. It just didn't occur to me (immediately) that what set this bloke apart wasn't that he was 'incompetent' and unable to match the results of the others. It was actually the case that he was the only one telling the _truth_ and could back it up with actual results. He was far more interested in me getting the right result and saving me from flushing money down the toilet that he in fact talked me out of a couple of options. He could just as easily have said 'sure no problem' and sold me the gear, but he didn't.

I didn't know at the time, but not long after that, his son burst onto the scene and is now a very successful race driver - household name in Australia. The guy was Craig Lowndes father, who was (way back then) running a workshop called 'northern tuning service'

Point being, it's not the guy with the biggest 'claim' it's the guy that can actually produce the result. Often their power figures will be 'lower' (but they are real not imaginary) . they won't be the cheapest mob out there (but ironically they won't be the dearest).


If the guy meant he could put together a turbo or supercharged combo that would produce 225bhp then that is doable for sure, but it'd still be over the top for a streeter.

in very general terms, I'd reckon 100bhp per litre would be about the maximum you could get out of a motor and have it realistic enough to last on an a series based non turbo streeter. I'd also point out that the wilder the motor, the more you need to change diff ratio to make it work (and the more and more you'd need a closer ratio gearbox) Which means that highway cruising rpms will be higher than is ideal, so it limits just how streetable the motor is.