OK I'll start with Full race A15 SCCA GT-Lite car, 156 HP at the wheels. I would expect stock A15 to be 50-55 at the wheels.

Next my A12GX engine with 10-1 compression, ports cleaned up and manifold gasket matched, FCR flatslide carbs, 280 duration .460 valve lift, header, 14lb flywheel is no at about 80 WHP (with GX cam was 73 RWHP). Mostly used parts except rings bearings and Gaskets. Cost $1268

My A15 build is going to be around $1500 give or take a $100. I'll be using the GX head with FCR carbs and header off the A12, I picked up used JE piston set from PJZ, will send cam out for regrind (both cams I have are single gear) The goal is 100 WHP or better, but keep the motor making power in the 3000-7500 range instead of A12's 4500 - 8200.

Just to rough out some numbers:

If you clean up the ports yourself, use the thinner GX head gasket, have the cam reground, and add a used weber DGV style carb I'd bet you would add 12-15HP over stock. 70 at the wheels? Shop carefully and figure $600.

Next jump would be adding some pistons to up compression around 10-1 and finding some side draft carbs of some sort, I managed to find my flat slides with manifold cheap even with extra Jets and dyno run it only added up to $400. If you can find a $100 set of used pistons as I did and they fit without machine work, you could get to the 100 WHP mark the $1500 as I've planned.

Getting beyond on that will start to get very expensive, I would expect past the 100-110 RWHP mark to start costing $800-1000 for every 10 horsepower. (full race engines easily cost 10K)

My numbers don't factor in any labor as I do my own work.................I would expect the labor to double the cost, if not more.


My opinion, 120 WHP max for a street car (non turbo), beyond that and it probably would suck in any kind of traffic.

For fun I'll say the Holy Hand Grenade of Antioch Turbo Rod Flinger A-series top fuel drag motor probably could make 180 at the wheels maybe even 200................if you could bear watching $15,000-30,000 engine go kablamo.


Tom

Nick Bone NZ. Is claiming 207bhp from his A15 race car http://www.no8online.co.nz/webpage.php?id=78

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Bige in my eyes locked dizzie is done and proven no need for complicated ecu or electronics.

A12T or A13T well tuned with 80 to 145hp atw using drawthrough setup is all thats needed for our light little jiggas. Beyond 150hp then EFI and strengthening measures are needed to withstand beyond 200% original output they are designed for.

Gearboxes also become and issue all costs then skyrocket even with a big hp NA A series gearbox choices are oftern overlooked as they are pigs to drive on the street. With 80-145hp atw stok 4 speeds are good enough with a decent clamping clutch. The torque they produce dont require close ratios saving a big wad.

eg. a12 69hp -> 120hp ate, a13 75hp -> 150hp ate, a14/15 80hp -> 160hp ate

For me the torque that turbos produce is much more appealing than hp.

Torque is HP -- HP at a specified RPM.

69HP is all thats needed for our light little 1200s.

69 is a good number :)

If people want to have a crack at this NA a15 stuff - count me in. I've been working round the clock in the last 6 months (new job, love it) and slowly stockpiling parts for the supercharged a15 buildup.

however - I picked up 2 a15s from 'clubman' (I won't use his name here without his ok) who used to have them powering his racer. He's moved on to sr16 power (and power it has aplenty for what would be a close to stock setup, with tweaks to induction and exhaust mainly, but stock internals)

Anyway - amongst the bits are a heavily ported oval port head. It's been shaved for higher compression, so probably won't go on my supercharged setup. I'm happy for someone to use this as a test bed head or whatever. Maybe we can all bring enough ingredients to make decent soup, so to speak.

I think I can also get a std bore a15 block (but just the block and caps) - it's from an a15 I sold some time back, but the buyer used the internals in an a14 block based combo. He's indicated he'd be willing to part with it for a price to be determined, so I'm planning to grab it, whenever I can find the time to catch up with him and seal the deal.

I've also gotten a cam approximately the same (varies by a couple of thou lift and a couple of degrees, so likely within a couple of kw) as the 140 profile on this page http://tighecams.com.au/profiles3/nissana12.htm

(but I must stress it is not from tighe cams, just happened to be a convenient online link that happened to have almost identical profile)

I suspect it might be a touch too mild for this build, but it probably isn't ridiculously out of the running.

I don't have any webers or twin weber intake manifold, but I can lend a set of 4 into 1 headers, that would be close to ideal primary diameter for this project (and possibly just a bit shorter than ideal primary length, but again, not out of the running, and primary diameter is far more critical than length)

There's a set of FCR carbs I'm buying from D (if i can ever arrange a time to actually catch up with him, pay the money and grab em!)

What else - I dunno - a flywheel or two and other bits and pieces, if needed. Going by how busy work currently is, i can loan these parts out for a considerable period of time.

Jmac Pm sent

How were you going to drive the blower John?
I have a few scratch built front pulleys here. Steel center hub, with a custom alloy pulley. You'd need to make a pulley to drive you blower. But it'd give you a starting point. They are a little bit heavier that the stock front pulleys. But the stock pulley's dont really lend themselves to being adapted to drive anything. Plus I've seen heaps of the split/slog out through the keyway.

I was planning on starting with the seemingly less common dual belt front pulley. I only know of them as they were on the previous a15 i had. It seems everyone likes the single pulley (which also has triangle or 'piece of pie' shaped holes around the entire hub section. I suspect for lightness What i planned was simply drilling and tapping the double pulley one, and using the pulley from a belt driven OHC setup (which due to their 'offset' will allow it to sit over the top of that outside smaller diameter pulley section and dowelling it in place (referenced from the centre somehow, with a piece of round bar turned down on a lathe) and then bolting the two together (mspaint on request).

This heavier less desired (by the NA crew) pulley would be stronger, and should hold up.

I am aware of the cracking issue, and I'd suspect it is partly due to the lighter weight of the pulley and the rpm it may be subjected to.

I'm hoping I won't have to adapt a fluid filled style damper but don't 100% rule it out. It will certainly fix the cracking issue. I do also know a bloke who is a magician at repairing cracked pulleys, so there's alway that option if need be.

In my case, I want the heavier pulley to start with (and am certainly not against the idea of a custom one).

Using the 'cam belt' and pulleys limits the drive ratio to either 1:1 or 2:1 (or 1:2 if it were put on a sub 1 litre engine I supppose) - using either 2 cam pulleys, or one crank and ne cam pulley.

I plan to run without the electromagnetic clutch, and have it running all the time. So the toothed belts won't cause an issue on that front. The reason i planned for that is that the first sc14 I picked up, which is in good condition, came cheaply as someone had buggered the clutch and then locked it solid with screws through the pulley/hub to lock them together. I planned to delete the clutch altogether and just run the toothed pulley. It's been done before:

This pic was on a geocities site, all of which were closed down a few years back, I happened to have it on the harddrive - so I'll upload here




Obviously there are otber issues on the pictured s/c drive setup pic that I would tend to avoid - for one thing the huge roller coaster, loop the loop intake tract - for a second, intercooling after the s/c (actually that isn't pictured in that pic, they put the cooler on later) They had it (at the end) on a 2:1 drive ratio - and were spinning the motor to something like 5500rpm (therefore 11,000 blower rpm). The a15 is less than half the size, so presumably a 1:1 drive ratio would give good boost, but also not push blower rpm too high

The cam/crank pulleys on any specific engine will only allow a the mentioned 1:2 1:1 and 1:2 drive ratios. What I _am_ wondering is whether there happen to be standards when it comes to toothed belt tooth size and gap - so that the pulleys from some other engines occasionally have the same tooth size/spacing. Maybe it could get really lucky and (for arguments sake) the one set had 40/20 teeth, and another had 30/15 teeth on the cam/crank sprockets specifically - then mixing a 30 and a 40 give a 3:4 or 4:3 ratio - or simplified to a 1.33:1 or 1:1.33 drive ratio - or whatever the numbers may be. I don't know that this actually occurs, but if it did it'd be fantastic to find and document which engine/models had compatible pulley tooth spacing/sizes and a tooth count for each so everyone could go about tailorin their boost levels with stuff from the wrecking yards.

If that was a no go, I'd also look into the 'gilmer belt drive' conversion sets. They aren't great for alternator and water pump bearings as they move the pulley forward to clear the existing fan belt/groove areas - loading the bearings due to far more leverage But on a s/c - where you _want_ it to clear the alternator/water pump belt, and leave it intact, _and_ the blower pulley fitment can be close to the front of the casing, no exacerbating effects/premature wear of the s/c bearings. So that _might_ be the other place I'll look.

So I plan to run it constantly driven, and drawthrough (on lpg, since I know lpg stuff like the back of my hand, and due to price per litre - it's slightly higher octane than pump fuel, but with varying butane content, not astronomically higher, at least not any more afaik, though I do note a couple of places do sell 100% propane) -

Anyhoo - there seems to be 2 schools of thought as to why these blowers expire (aside from just trying to spin them at a way too high rpm or boost level that nothing would survive) - either it's being 'on' too much and they just eventually deteriorate in condition under the stress. The other one I've heard put forward is that direct driving them and having them running all the time, at part throttle with barely any air passing through to cool them is an issue. But I'd counter that by saying if the air density is very low at part throttle, there's less effort/stress/compression happening in the blower casing, and it won't heat up (beyond heat conducted through the manifold(s) attached to the engine and some convection) at part throttle anyway.

In any event, I do have a spare low mile sc14 with a good clutch so if the whole thing expires in a month or two, I'll swap in the new blower and re-vise the intake/blower switching ability to sort it.

Being a dry fuel metered in in gaseous state, the lpg won't have any cooling effect on the blower rotor/lobes, but it also won't have any solvent like effect that might compromise the surface layer(s) of the blower lobes which should be a good thing. I plan to run water injection, and do so pre-blower, so that it might have some (limited) cooling effect on the blower at higher boost levels, where it might be heating up. As long as it is introduced as a fine mist (rather that a solid jet/stream of water like very eariy turbo water injection setups had - that were sometimes aimed at the SU carb needle, or the holley booster venturi region to try and atomise it, or if all else failed it'd happen to some extent at the turbo compressor wheel region) - so anyway as long as it is a fine mist, it should be ok (or at the very least, it won't do any harm)

Lpg doesn't experience 'dropout' through tight bends like liquid fuels to, so in that regard, I can get a little bit tighter with the bends from lpg mixer/carb to the supercharger inlet and to a slightly lesser extent from supercharger to intake manifold. (that being to a lesser extent owing to the fact it'd have some water mist in there at that point when it sees enough boost)

A14force - if I can't manage to get a factory based pulley to survive, I'd be very keen to buy one of yours. Out of interest - what sort of money would you be after for one? and what belt type is it to suit - traditional v belts, ribbed belts, toothed belts?

$100+postage.
I used to be able to get custom made 5pk pulleys made too. (See mine under my profile) but the hook up for free aluminum has come to an end.
I'd post a pic, but I'm having trouble with the camera atm.

Also FWIW, I run an S/C14 at 1:1 on an A15 with a big cam and some port work. (And stupidly oversizewd inlet valves) and it make 10-11psi