small tweaks to achieve more power

Any form of normally aspirated power mods.
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small tweaks to achieve more power

Post by 350matt »

Chaps

I'm in the process of rebuilding my lump and I have few ideas to improve power and would welcome your thoughts

1) bypass the water heating for the throttle body - this is added by OEM's to help with cold start emissions and fuel 'icing' in cold climates
not really required in the UK and a colder inlet should be worth a couple of ponies

2) port the throttle body as its a little undersized for this level of airflow (by calculation), there's a few sharp edges on the entry and knife edged butterfly and thinning down of the cross shaft should yield some gains

3) lighten the rotor's, as with piston engines, lower reciprocating mass is worth power ( only a small amount) I'e yet to get my engine down to the bare bones but I'm sure there's a few areas that be trimmed

4) porting - a well travelled topic, I'll be attempting my own 'street port' and am considering a radiused exit of the port into the chamber but the images I've seen to date all have a sharp exit?

5) apply a low friction coating to the rotor side plates ( on the induction area )

6) fit a low temp thermostat to again increase VE
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Re: small tweaks to achieve more power

Post by PeteH »

350matt wrote:Chaps

I'm in the process of rebuilding my lump and I have few ideas to improve power and would welcome your thoughts

1) bypass the water heating for the throttle body - this is added by OEM's to help with cold start emissions and fuel 'icing' in cold climates
not really required in the UK and a colder inlet should be worth a couple of ponies

2) port the throttle body as its a little undersized for this level of airflow (by calculation), there's a few sharp edges on the entry and knife edged butterfly and thinning down of the cross shaft should yield some gains

3) lighten the rotor's, as with piston engines, lower reciprocating mass is worth power ( only a small amount) I'e yet to get my engine down to the bare bones but I'm sure there's a few areas that be trimmed

4) porting - a well travelled topic, I'll be attempting my own 'street port' and am considering a radiused exit of the port into the chamber but the images I've seen to date all have a sharp exit?

5) apply a low friction coating to the rotor side plates ( on the induction area )

6) fit a low temp thermostat to again increase VE
1) Why not! I suppose I should do that as well. Although I bet it's only worth about 0.1bhp.
2) Can't hurt. There is a thread on here about someone trying it. I'm not sure I agree that the throttle body is small for the flow though. When I did the calcs I thought it looked like more than enough. I shalln't be doing this one, because it's a lot of effort for almost zero gain. But if you have the time then sure. (If you do think the throttle body is too small, then fit a bigger one)
3) You can lighten the rotors. It's a standard "trick" for tuners. But the RX-8 rotors are the lightest Mazda have ever done. You won't get more power from lightened rotors, and you will get much bigger inertia gains from a lightweight flywheel. But if you plan to raise the rev limit then lighter rotors can help a lot, by reducing stresses on everything.
4) Yep, porting! There's no shortage of info on this one. For info, ports have sharp edges for a reason. The port edges define the port timing. If you radius the edges you won't improve flow (the gas wants to go straight in, it doesn't want to curve round), but you will radically alter the port timing. The net result would be all the downsides of wild port timing (poor low speed running, high idle, poor low speed efficiency etc), but none of the benefits of high flow. If you are happy with wild timing then make the port area / volume as large as you can for maximum flow, and that means square edged ports. You also have to be very careful that your seals don't fall down the port edges, which is another important reason for square edges. You will see some "corners" on the ports as well. These are also important, for the same reasons.
5) To what purpose? The side plates are already coated with a hard / low friction thing. Some people do go to the effort of ceramic coating, but generally only on top end race engines. It's a durability mod, not a performance mod.
6) I never understood that one! You don't get a more dense charge from having a cold engine "block". The air is already in before it knows about the engine heat. Low engine temperature causes more heat transfer from the burnt mixture, which reduces thermal efficiency. This is why cold engines run rich. There is a reason engines run at the temperature they do, and a reason why manufacturers try to get them hot quickly...

I have a feeling you know most of this already (and know people that do). So I'll be interested in your response.
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Re: small tweaks to achieve more power

Post by 13Black »

Well, as someone who understands physics applied to the automotive industry, I'd have thought you'd have a few tricks up your sleeve :D

Coolant bypass yes.
Lightning rotors yes, very minimally, not sure how you'll go about balancing everything as a one off, just outsource it surely.
Porting, can get templates but if you have some ideas, you might know something most of us don't. As long as there are no burrs sitting proud, that should do.
Coating things, nah I wouldn't have thought there's much to do here that would make things worth the effort.
Increase the oil pressure while you're in there. Yes it'll have a negative effect on power but it's worth while.
You can port the auxiliary port valve/sleeves supposedly. Have a look and see what you think.
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Re: small tweaks to achieve more power

Post by warpc0il »

350matt wrote:Chaps
I'm in the process of rebuilding my lump and I have few ideas to improve power and would welcome your thoughts

1) bypass the water heating for the throttle body - this is added by OEM's to help with cold start emissions and fuel 'icing' in cold climates
not really required in the UK and a colder inlet should be worth a couple of ponies
Modern pump fuels are particularity susceptible to icing as they aerosol, even at ambient temperatures way above freezing, and the effect is made worst in damp weather - so the UK is actually much more prone to throttle body or carb icing than most countries. Ask anyone that has had to use an anti-icing additive in an air-cooled VW engine or motorcycle. When these fuels were originally introduced, many motorcycle manufacturers had to produce carburettor heating kits to be retrofitted under warranty to stop engines suddenly and dangerously loosing power.

In short, removing the water heating is a bad idea. It isn't there for emissions, unless you count not suddenly sh*t yourself when you pull out of a junction and find your engine without power when you most need it.
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Re: small tweaks to achieve more power

Post by 13Black »

LC rebuilds have been running TB bypasses for years though Dave. I'm not aware of any issues they've had.
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Re: small tweaks to achieve more power

Post by warpc0il »

It's one of those things that you might get away with 90% of the time, or even 99.9% for cars only driven in warm dry weather.

Even when it causes a problem, you wouldn't know that it was the cause. There would just be a short sudden loss of throttle response, then everything would go back to normal.

Throttle body icing is less likely than carb icing as the tb is well away from the point of fuel injection but there's still a sudden drop of air pressure immediately behind the butterfly valve, which creates a fog - much like you sometimes see in the low pressure air above an aircraft wing.

Image

If the air is already cool and the humidity is high, then ice crystals can form in the fog and/or on the surfaces of the fb, which can cause the valve to stick. The water jacket keeps the fb warm enough to ensure that this isn't a problem, while not adding any significant heat to the intake charge.
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Re: small tweaks to achieve more power

Post by Dr. FrankenRex »

TBH, given the speed in which the air is going in to the engine, I can't see the water jacket adding that much to the intake temps. That said, I'd be interested to see any results.

Lightened rotors are a thing, as has been said, but they are many earth-pounds - RacingBeat rotors are $2,400 for a pair... If you can make perfectly balanced, reliable, lightweight rotors for less than a lot of cash, then you could make a tidy penny sire.
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Re: small tweaks to achieve more power

Post by PeteH »

Some of our friendly specialists on here can lighten the rotors for you (I assume they outsource). I don't think they charge anything like RB prices.

Looking at the throttle body heating thing. If the coolant really did pass significant heat to the intake air then the coolant would also be getting significantly cooler. Perforce, if you bypass the TB cooling circuit then the engine coolant should run hotter. That wouldn't be a brilliant idea on our engines. Fortunately, I agree that the amount of energy that can be passed from the coolant to the inflowing air must be the square root of naff-all, so we probably shouldn't worry about it.

(I'm going for a word of the day here, by the way, Dave :lol: )
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Re: small tweaks to achieve more power

Post by zippyonline »

PeteH wrote: (I'm going for a word of the day here, by the way, Dave :lol: )
Good idea, I'm going to join in :P

So basically, with the coolant running through the TB, altering it, the juice isn't worth the squeeze.
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Re: small tweaks to achieve more power

Post by warpc0il »

"Perforce" is being overtaken by "Git" in many arenas :)
[urlw]https://www.atlassian.com/git/tutorials/perforce-git[/urlw]
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Re: small tweaks to achieve more power

Post by PeteH »

warpc0il wrote:"Perforce" is being overtaken by "Git" in many arenas :)
[urlw]https://www.atlassian.com/git/tutorials/perforce-git[/urlw]
That's genius Dave! :thumleft:
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Re: small tweaks to achieve more power

Post by Essex2Visuvesi »

Used to have carb icing issues on my R5 GT Turbo with a Huge Front mounted intercooler
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Re: small tweaks to achieve more power

Post by boosted »

Yep my 5 turbo used to buck a roo down the road.

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Re: small tweaks to achieve more power

Post by 350matt »

thanks for the responses guys

I agree T body heating gain will be small but I've seen it work before and with no ill effects,
regarding a lower coolant temp then this generally lowers combustion chamber temperature as the metal temp is lower and as a consequence you do get a VE gain and also gain a little bit of det resistance, I've done this on many engines and it nearly always works - of course this triangular buzz bomb isn't a normal engine, so it may not work in this case.

OEM's run hot for emissions and fuel economy its not for power, 82 deg C is the best water temp for power and I think the Renesis stat opens at 80 I think so the running temp will be about 88-90? I don't have any data on this though if its already at 82 then great.

regarding the side plate coating do you know what it is? I know the housings are a hard chrome onto the ally but I thought the side plates were a raw cast iron that was polished up?

regarding porting are there any references you can point me to?
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Re: small tweaks to achieve more power

Post by warpc0il »

When it comes to cooling, there's a major difference between any piston engine and a rotary...

With a piston engine the incoming charge is drawn into the same chamber that has just ignited and exhausted, thus cooling those components, particularly the cylinder wall and the head.

With a rotary engine there are dedicated sections for intake, compression/ignition and exhaust, and that's all they do, over and over, very rapidly, with no relief in between.

The side and centre irons are "processed with soft-nitriding for improved wear resistance of the rotor friction surfaces".

Before you start to strip and rebuild, you may like to take a look at this
http://www.rx8ownersclub.co.uk/forum/vi ... 58&t=60547
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Re: small tweaks to achieve more power

Post by Shagrington »

350matt wrote:.... 82 deg C is the best water temp for power and I think the Renesis stat opens at 80 I think so the running temp will be about 88-90? I don't have any data on this though if its already at 82 then great.....
My gauges usually show coolant at 82C in normal running on clear roads. :thumleft: It rises in different circumstances like traffic etc.
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Re: small tweaks to achieve more power

Post by 350matt »

thanks for the info chaps

a nitrided surface is whats used on a high performance crankshaft bearing surface, its great for wear resistance but doesn't offer much of a friction benefit over a polished surface

I was thinking of applying some of this

http://www.fluoroteccoatings.com/materi ... 0wodlPENrw
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Re: small tweaks to achieve more power

Post by PeteH »

That's a soft plastic coating with a tensile strength of about 35N/mm^2 (about 5% of a decent metal coating). It also has a maximum working temperature of about 280degC. It's primarily used to add corrosion protection to bolts ect

Why try to reinvent the wheel? Mazda have spent decades on this.

I admire your ambition, but I'd suggest you read up on rotaries first, and try your ideas "in private". When you find things that work I'm sure we'll all be very interested.
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Re: small tweaks to achieve more power

Post by 350matt »

I'm not trying to re-invent the wheel
Mazda had to make concessions to mass manufacture just like any other engine manufacturer

so small detail changes like this do tend to add up
you don't find 10Bhp you find 1Bhp ten times

and xylan is used on piston skirts hence my consideration of it

http://www.whitfordww.com/industrial/ca ... -wear.html

perhaps it would be better applied to the rotor sides instead

and yes I'd love to read up on rotaries any suggestions of suitable texts?
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Re: small tweaks to achieve more power

Post by PeteH »

I was probably a bit too negative in my post. But I guess the reason for posting your ideas is to get opinions on them... ;)

That link is to an air piston, not the piston of an internal combustion engine, so the temperature and stress regime is very different. I still wonder about the durability of that coating when it's anywhere near the chambers of a rotary. The problem is, if it comes off it could do lots of damage, so you'd be running a risky test. I also wonder if that coating is oleophobic (I'm determined to get a word of the day Dave ;) ). If the coating doesn't like oil then you might do more harm than good. Putting it on the rotor sides should be a waste of time, because the rotor sides don't touch anything. Only the seals contact the housings.

Having read that web site I can see why you might be interested in looking at Xylan, but none of the application examples look any near the duty cycle of a rotary engine to me.

As for reading matter, my suggestion would be "Street Rotary" by Mark Warner. He does a great job, and covers most of the tuning opportunities available to rotaries. There are other books that actually describe the rotary in more detail, but Warner's book is by far the best for understanding how to get the best out of it.

Let us know how you get on. :thumleft:
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Re: small tweaks to achieve more power

Post by 13Black »

Street rotary is fun but I haven't felt that I've gained anything really practical from it. But I don't know. The idea of milling fins into the coolant passages near the l exhaust port looks nifty however.
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Re: small tweaks to achieve more power

Post by warpc0il »

=D> and our word for the day is "Oleophobic"

Who would have guessed that word would have been used, in context, on an RX8 forum :shock:

Everyone knows that 8s are oleophilic , actually that would make quite a good forum name :thumright: ,
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Re: small tweaks to achieve more power

Post by Dr. FrankenRex »

My other thought, having re-read the posts along with the newer posts is that you might find one or two bhp, but I imagine that the changes will all amount to a fair amount of cost for the gains made.

a 1hp increase is all well and good if its cost is relative. I'd expect to pay more for a 10bhp increase than a 1bhp increase, but I wouldn't pay ridiculous amounts for either...

That said, mine is a road car, not a race car
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Re: small tweaks to achieve more power

Post by warpc0il »

The easiest way to improve the power:weight ratio is just to go on a diet*

*says he, having put on 10kg in the last 18 months #-o
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Re: small tweaks to achieve more power

Post by zippyonline »

#MarginalGains
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