Supercharged b310

[SunnyPower]

Wow, five years have passed since my last post, been kinda busy I guess...

 

So, greets from Finland once again. Sunny has gone through some trashing and wrenching. Some include massive rust repairs and diy paint jobs, some suspension & engine work.

 

It received my old a14 motor from crashed b310, where I slapped blower and stuff next to it. With current drive ratio it makes around 9-10 psi boost immediately. Hp don't know, torq plenty compared to stock n/a 😄

 

Sadly its currently sitting with fried piston rings, I'm building two engines atm. a12 n/a with cam/head/extractors and carbs to get it mot'd and a a15 bored with new pistons etc.

 

Journey continues, feel free to ask questions

 

[datzenmike]

My A14 was (I think) about 68 hp. Ten pounds is (very roughly) 68% increase in air pressure so 115hp over stock. Many car makers have turbo'd their engines and on stock hyper eutectic pistons* they limit boost to 6-8 PSI and they live forever. When rebuilding, keep in mind that you're making almost 70% more of everything including heat. The top ring is going to get extremely hot and it will expand. Enough that the stock ring gap will close. This easily will cause the ring and/or the piston ring land to break.

 

Top ring gap...

Stock gap is 0.004" X bore (76mm or 2.994") = 0.119"

SC gap is 0.006" X 2.994 = 0.1786"

 

The extra 0.00598" allows more room for expansion.

 

Second ring gap is also 0.006" x bore.

 

* Hyper eutectic pistons have 12% to 20% silicon content (glass) making them extremely hard but brittle. They don't expand much when heated so the bore can be tighter and they are quiet on start up when cold. If the pistons need replacing you might consider getting forged. These contain little silicon and do expand when heated so require larger bore clearance and are not so quiet on cold start up. The are tougher and absorb punishment much better in turbo or SC applications.

 

 

Is that a Stromberg carburetor?

[SunnyPower]

8 minutes ago, datzenmike said:

My A14 was (I think) about 68 hp. Ten pounds is (very roughly) 68% increase in air pressure so 115hp over stock. Many car makers have turbo'd their engines and on stock hyper eutectic pistons* they limit boost to 6-8 PSI and they live forever. When rebuilding, keep in mind that you're making almost 70% more of everything including heat. The top ring is going to get extremely hot and it will expand. Enough that the stock ring gap will close. This easily will cause the ring and/or the piston ring land to break.

 

Top ring gap...

Stock gap is 0.004" X bore (76mm or 2.994") = 0.119"

SC gap is 0.006" X 2.994 = 0.1786"

 

The extra 0.00598" allows more room for expansion.

 

Second ring gap is also 0.006" x bore.

 

* Hyper eutectic pistons have 12% to 20% silicon content (glass) making them extremely hard but brittle. They don't expand much when heated so the bore can be tighter and they are quiet on start up when cold. If the pistons need replacing you might consider getting forged. These contain little silicon and do expand when heated so require larger bore clearance and are not so quiet on cold start up. The are tougher and absorb punishment much better in turbo or SC applications.

 

 

Is that a Stromberg carburetor?

 

Hi mike!

 

Yes, around 100-120hp is close to what I've calculated it should be making. I've run stock ring caps, keeping the engine cool with upgraded radiator and electric fan setup, also the fuel charge cools down the blower pretty nice. Rings got fried over a head gasket blow, and the motor got extremely hot. In that same mishap, the ring grooves got f*cked, so the pistons are garbage now. But ay thats all about this hobby aint it ;D

[datzenmike]

Upgrading the cooling system is a good start but the heat is very concentrated in the piston top and relies on conduction through the cylinder walls to the coolant. It can easily over heat faster in the short term than it can be removed. As oil gets to places the coolant doesn't an oil cooler might also be used.

 

The block is going to have to be over bored what ever pistons you decide on. A good idea for an SC engine is to have the block O ringed to contain the compression and save your head gaskets. An ARP stud kit to replace the head bolts will also go a long way to preventing blown head gaskets. While you are at it ARP rod bolts too as the A 14 really likes to rev. A 77mm stroke is good to 8,000 RPMs on stock parts but in all fairness the weakest link are the rod bolts.

[Stoffregen Motorsports]

Pretty cool little car. Did you mention where the supercharger came from? Something British, I assume.

 

I agree about the ring gap, it needs to be increased to be able to handle the boost.

[Anonymous Waffle]

On 12/26/2022 at 9:34 AM, Stoffregen Motorsports said:

Pretty cool little car. Did you mention where the supercharger came from? Something British, I assume.

 

I agree about the ring gap, it needs to be increased to be able to handle the boost.

 

I believe that's one of those mini roots blowers, probably the AMR 300. It's been pretty popular recently for "low-buck" supercharging. 

 

I have no clue if it's a general aftermarket application or if it's original purpose was a smog pump or not. It's very similar to the porsche 912 smog pump from the late 60's that was then used by the VW beetle guys for baby superchargers. I always wanted to supercharge a mini-bike with one of these hah.

[datzenmike]

Every turn of the engine draws 700cc displacement so how much air is displaced by the SC? Would have to be more than that, or spun faster than crankshaft speed.

[Stoffregen Motorsports]

There is also an AMR500 supercharger, which is slightly bigger.

[Dguy210]

http://datsun1200.com/modules/mediawiki/index.php?title=Forced_Induction

 

For the OP as it goes in depth with lots of builds.

 

 

16 hours ago, Anonymous Waffle said:

 

I believe that's one of those mini roots blowers, probably the AMR 300. It's been pretty popular recently for "low-buck" supercharging. 

 

I have no clue if it's a general aftermarket application or if it's original purpose was a smog pump or not. It's very similar to the porsche 912 smog pump from the late 60's that was then used by the VW beetle guys for baby superchargers. I always wanted to supercharge a mini-bike with one of these hah.

 

2 hours ago, Stoffregen Motorsports said:

There is also an AMR500 supercharger, which is slightly bigger.

 

 

Checking the price on those AMR300 and AMR500s I can't believe those are that cheap (~$200-300).

[datzenmike]

18 hours ago, Anonymous Waffle said:

 

 

 

I have no clue if it's a general aftermarket application or if it's original purpose was a smog pump or not. It's very similar to the porsche 912 smog pump from the late 60's that was then used by the VW beetle guys for baby superchargers. I always wanted to supercharge a mini-bike with one of these hah.

 

Smog pumps don't need anywhere near that volume of air or pressure. The L20B 'smog pump' produces less than 1.9PSI and almost no volume. What little unburned hydrocarbons that do exit in the exhaust only need a small amount of oxygen to burn.

[Anonymous Waffle]

10 hours ago, datzenmike said:

 

Smog pumps don't need anywhere near that volume of air or pressure. The L20B 'smog pump' produces less than 1.9PSI and almost no volume. What little unburned hydrocarbons that do exit in the exhaust only need a small amount of oxygen to burn.

 

 

Them Germans in 1968 thought that a roots style "air pump" was needed to smog their 912s in the U.S. Guess it caused cylinder head cracking due to the air injection so it was fixed the next year in 69. Not too much information out there, but its an interesting read in here. 

 

https://www.912bbs.org/forum/threads/my-1968-porsche-912.52121/page-2

 

Also this is a good lil watch on a 420cc predator engine with a amr300 supercharger, swapped into a honda insight. 

 

 

 

Edited December 30, 2022 by Anonymous Waffle

[Stoffregen Motorsports]

21 hours ago, Dguy210 said:

Checking the price on those AMR300 and AMR500s I can't believe those are that cheap (~$200-300).

I noticed that too. Really makes me want to buy one and put it on my Sprite, or my Farmall Cub tractor. What else do I have laying around...???

[SunnyPower]

Yes, this blower is an aisin amr500 out of Nissan march turbo, 0,5L per revolution 🙂 Its overdriven around 2.1:1, making 9-10 psi in a a14 engine

[datzenmike]

Very nice. Produces 2,100cc of air for a 1,397cc displacement engine. That's 0.665% more air than needed or X 14.7 = 9.79 PSI (theoretically 116 hp) Adds up nicely.

 

Lots of turbo engines in mass production here were conservatively in the 6-8 PSI range and they live forever on stock hypereutectic pistons. Did you do anything to the engine to increase the longevity? such as increased ring end gap, forged pistons, ignition retard, oil cooler, water/alcohol charge cooling, cold air intake?  

[SunnyPower]

1 hour ago, datzenmike said:

Very nice. Produces 2,100cc of air for a 1,397cc displacement engine. That's 0.665% more air than needed or X 14.7 = 9.79 PSI (theoretically 116 hp) Adds up nicely.

 

Lots of turbo engines in mass production here were conservatively in the 6-8 PSI range and they live forever on stock hypereutectic pistons. Did you do anything to the engine to increase the longevity? such as increased ring end gap, forged pistons, ignition retard, oil cooler, water/alcohol charge cooling, cold air intake?  

No need on any of that. We have run these with 15psi over with stock ring caps, rods, pistons etc. for years. Just don't let it PING or it WILL detonate lol. No need for coolers where I live, just run a proper grade oil.

 

Ignition is set safe zone around 25btdc and is locked there. As the boosted fuel charge (I'm running 50% e85 mixture with regular) runs through the charger and the intake, theres no need for a cold air intake etc. The pipe right on the carb will generate ice on it even on summer days, so thats free intake cooling. Physics are awesome

 

Cheers, sunnypower