Increasing Engine RPM

[RSmith]

I have a small 700cc 3 pot turbo engine in the back of my smart. I love it... but I can't help thinking it has higher RPM potential. It cuts out at 6,500 rpm... what modifications would be needed to get it up to... say 10,000 rpm?

As far as I can think... a better cooling system, stronger valve springs, bigger valves and ports to bring the powerband up and forged pistons. I'm sure there's a lot I'm missing

NB: I smacked my gob when I searched in google for "How to increase engine RPM". ONE page came up. ONE! Try it in quotation marks!!!

 

[HDi fun]

Dynamic balance is the key if you want to use higher revs. 3 cylinder engines don't lend themselves to massives revs but a blueprinted bottom end (crankshaft, rods and pistons) will make higher revs more accessible. I doubt you'll get 10k as a red line but 8000 should be achieveable.

You mention valve springs. If you could fit double springs it would help massively in reducing valve 'bounce'. Stronger springs alone don't necessarily achieve this.

 

[RSmith]

Do 3 cylinder engines not rev well because they have to be internally balanced? Also... double springs would help, so, probably looking at a custom cylinder head on this one. The blueprinting... I know where I can get that done. Are there any other specific dangers to consider when cranking up the revs?

 

[Country Bumpkin]

There's plenty of thing to consider and plenty of hurdles but don't forget that to get those revs, if you have an engine capable of doing it, you will need the ingition map to reach it and the fuel increase to support that too.

 

[pgarner]

yeah a rod being thrown through the block for starters.

alot of balancing would be needed along with tight tolerances with bearings.
youve also got the amount of exhaust gas going through the turbo basically doubling up the amount of air 6.5k - 10k so youve got extra strain on it.

 

[RSmith]

Okay, so I've got map and increased fuel demand. If I were going to do this, I would ensure that every part of the engine was scruitinised. I would most probably fit a larger turbo with the existing one in a sequential bi-turbo set up to handle the increased rpm range and have it bought in line with a good map and pressure regulator. The smart's engine will only handle up to 1.3 bar.

Just to clarify... when you say "a rod being thrown through the block"... forgive my ignorance but how would it cause a rod to go through the block?

 

[pgarner]

with the engine spinning so fast and out of balance then there is a chance of it simply not going where it should.

remember the pistons are going up and down but trying to make this go in a turning action at the crank

 

[HDi fun]

I'm starting to think that starting with a minimum of 4 cylinders might be better

 

[RSmith]

I'm starting to think that starting with a minimum of 4 cylinders might be better

You're probably right. The only reason I want to use the existing engine is because I want to see how far you can take the smart car into high performance without an engine transplant... What if we were to look at this another way... motorbike engines like the Hayabusa 1300 can spin up to 14,000rpm with no apparent problems. What makes them so special and allows them to do that? Could the technology in that engine be used in my one?

 

[HDi fun]

IS it a diesel?

No forget that - can't be with 6500red line

 

[HDi fun]

Have a look at www.celtictuning.co.uk

The should be able to get some more power and torque from it

 

[BAD63R]

Could just drop a GSX-R 1100 engine in and give yourself a massive rev range. Seen it done before and can get some amazing resaults. Check the vid...

http://www.youtube.com/watch?v=YtWeSa3naKk&feature=PlayList&p=5392FF3A7B7442D5&index=0&playnext=1

 

[RSmith]

IS it a diesel?

No forget that - can't be with 6500red line

...No it's petrol. It's just got a stock remap that stops it wandering further. Besides, with the current setup it's out of torque after 6000. Please note that due to it being a city car, it's 2 valves per head and 2 spark plugs per head.

Could just drop a GSX-R 1100 engine in and give yourself a massive rev range. Seen it done before and can get some amazing resaults. Check the vid...

I know... I've seen the vids and I know a few people who've done it (smart community). But they eat clutches for breakfast, unreliable, expensive, and I'd like to test my skills as a modder without just opting for a transplant or some kit if that makes sense Please note I will also be toughening up and changing the ratios in the gearbox to compensate if the engine tuning is successful.

 

[HDi fun]

It's quite a tak that you're considering. The problem with a 3 cyl 4 stroke engine is that that the power stokes are interspaced with gaps. This leads to torque reversal which loads up the crankshaft.

Even with four there is no overlap. Things become more interesting with 5 or more cylinders. But I'm not about to suggest fitting a V6 to a Smart.

It would be quite something though if you could fit a PSA HDi V6 in there.

 

[RSmith]

The problem with a 3 cyl 4 stroke engine is that that the power stokes are interspaced with gaps. This leads to torque reversal which loads up the crankshaft... ...It would be quite something though if you could fit a PSA HDi V6 in there.

So, in 3 cylinder engines, why don't all three pistons reciprocate 120 degrees from each other to give a constant hum? I know I'm plunging into more and more ambitious waters but could you have a custom crankshaft to give said uniform spacing? Obviously, the cam and timing chain would then have to be custom too but that's all that would have to change. (Please be nice I'm only batting ideas around! :toung

Also... funny you should say that about the V6, I think there was a guy that biased his suspension and fitted a V6 or V8 in the place of the passanger seat. Could you imagine the noise?!

 

[HDi fun]

They are evenly spaced. But we're talking about a 4 stroke engine so there are gaps between the end of one power phase and the start of the next. (Each phase lasts for 180 degrees geometrically).

A full cycle is 720 degrees of crank rotation.
SO in a 3 cyl 4 stoke motor there are 60 degrees of crank rotation between the end of one power phase and the start of the next.