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pierre2212

Nissan a14 motor reaching 100kw

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Hi Guys i am new here on this Forum from South Africa.

I am building a Nissan Champ think it is called the b140.

i am rebuilding my engine to reach an output of 100kw to the wheels.

I am going N/A for this project.  

i do have a stoker kit for the A15 motor so i was thinking swapping the A15 crank and conrods and head over to the A14 block. I do have a 278 degree split cam( freaking nasty little cam)

what else can i do to reach 100kw? still on its stock carburetor. I was also thinking about boring out to 77mm piston size

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100Kw is.... over 134 hp!!!!  Is that even possible without a turbo?

 

Well the stock carb has to go. Individual throttle bodies or motorcycle carbs.

 

Longer stroke will reduce your red line from 8k down to 7.5K although it does give you 100cc extra displacement.

 

Definitely a header of some kind on a balls to the wall build like this.

 

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i know its a lot 😄 , yeah i am thinking about going to ITB's later on tho. Will it help if i do a stroker kit and a overbore on same engine? .Would just like to know if it is possible n/a otherwise i will try some turbskies

 

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Just increasing power 50% is a formidable and formidably expensive undertaking. 100% increase is optimistic. Longer stroke will limit how high you can rev to make HP but it does increase power at below that. There are other members that race the A series an can comment on this.

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A full race A14 will achieve about 160 hp at around 9500 rpm, so 135 with a street driven A15 is not going to be realistic. Not saying ti can't be done, but you're pushing the limits of driveability.

 

I've only ever built a couple A15's, mostly A12, A12A, A14 motors, but I am wondering how on earth you would fit an A15 crank and rods in the A14. The deck height on the A15 is so much taller. Even with a custom piston, and a de-stroked crank, it seems tight. Has anyone done it?

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Can always try to fit the a15 internals into the a14. See i would want to kbow if it will be possible or should i rather safe the money and time and get me a sr20 or 4age? Maybe 100kw was a bit optimistic 🙈

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The A15 and A14 use the same block with a deck height of 204.1mm, the A14 uses a 77mm stroke with a piston pin height of 32.5mm and the A15 uses a 82mm stroke with a 30mm pin height. They both use a 76mm bore.

 

As to the original question first I will share this; my so called race motor makes 99hp at the wheels. It uses a ported GX head with 39mm flatslide carbs, 278 cam, headers with 2 inch exhaust and 11.90-1 compression. It's streetable but uses 100 octane fuel. While the motor will run at any RPM it's happiest above 4500rpm and doesn't really make power until 5500 rpm.

 

Realistically 110hp at wheels is probably the turning point. 

 

A b140 makes all of 80hp at the crank stock (55-60 at the wheels?) so getting one up to 85-90 at the wheels is a huge improvement. 

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Will it possible to use the a14 pistons on the a15 crank and condrods? Because my a15 has a deeper dish in and my a14 has a slightly dish

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On 8/2/2018 at 6:56 PM, Tom1200 said:

The A15 and A14 use the same block with a deck height of 204.1mm, the A14 uses a 77mm stroke with a piston pin height of 32.5mm and the A15 uses a 82mm stroke with a 30mm pin height. They both use a 76mm bore.

 

 

 

A14/15s use the same rod length so yes.

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Okay cool just wondering which one would give best compression? The a14? 

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Pierre you will not be able to use the A14 pistons with the A15 crank because the pistons  will be sticking up 2.5mm above the deck. Not the previously mentioned piston pin heights, due to the 5mm longer stroke of the A15 Nissan decreased the piston pin height 2.5mm. You can mill the A14 piston down of course but that would likely lead to piston failure.

 

 

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Yup the rods are the same but the stroke is longer. Should have finished my coffee before posting.

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So here are some options to get the compression up.

 

Custom pistons; this is what I did. $600 for forged JE pistons with rings.

 

The standard A15 pistons come in a 6cc and 10cc dish and the head gaskets standard have a 1.2mm crush thickness. You can get a GX head gasket with a .8 crush thickness and a Nismo one with .6 crush thickness. Both available on EBay. Bprojects is on EBay (there a Japanese company that specializes in A-series stuff for Sunny models) You could get 6cc dish pistons and the thinnest gasket, I believe that will take you to 10-1 compression or close to it.

 

Honda pistons come in 76mm with flat tops / near flat tops; I can't remember if it's the D15 or B16 but you can look it up on the Internet. They Honda piston uses the same 19mm pin as the Datsun.

 

You can use Mazda MX-5 / Miata 78mm pistons, the small end of the rods will need to bore to 20mm and the piston tops milled flat. The issue with this solution is the compression ratio may be rather high for a street car. I don't know what head you're using, they vary from 29cc to 32cc combustion chambers and you would need to use one of those online compression ratio calculators.

 

DO NOT, DO NOT mill the head to get the compression up; this causes all sorts of issues with push rod lengths and rocker arm geometry. One of my cylinder heads has had 2mm milled off it and due to that I've had to fly cut deep notches into the forged pistons as well as make shims for the rocker shaft pedestals, as well as mill some of the pedestals. I have to mix and match the modified parts to get everything correct when every I fit different cams. It was a  pain to sort, luckily I have a machinist friend who's able to make these little custom bits. It's one thing to do it for a race car but quite another for a street car. 

 

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