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Romans 2005 Toyota Echo - Exhaust in progress / new big block setup


Roman

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Glad you are messing with outboards again. From what I read pretty much all the gains are from the charge cooling from the fuel phase change. They dont put them on bikes and race cars for zero reason. I mean we have old mates beams as a IRL example, he picks up like 10hp on his beast motor with 80-90% outboards, I just made that up beacuse CBF looking but its close to that. Most race car shit will run heaps of fuel pressre and spendy injectors to make it all work real nice.

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Yeah I guess I can do some dyno testing with bonnet up and then make some decisions from there. 

Will also print another revised version with injectors lower again. But hopefully get a decent spread of fuel under/over the throttle plate. 

The BMW airbox turned up today as well. It's super cool with the dual stage trumpets... But also definitely does not fit. 


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Speaking of such things. Guess what I saw last week. 
A Quest4 built EP82 drag starlet with a 3SGTE. 

Car was never finished but the whole front shell came off, but then the whole motor and trans was mounted in such a way you could swap out the whole front.
So they could race it in NA and turbo class just by swapping the front. 
Should have grabbed a picture, it was quite cool.

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12 hours ago, Roman said:

Speaking of such things. Guess what I saw last week. 
A Quest4 built EP82 drag starlet with a 3SGTE. 

Car was never finished but the whole front shell came off, but then the whole motor and trans was mounted in such a way you could swap out the whole front.
So they could race it in NA and turbo class just by swapping the front. 
Should have grabbed a picture, it was quite cool.

Kyrie is a very clever dude. He was talking years ago about building a st202 celica drag car with a Subaru gearbox with a 3sgte hanging off the front of it like the American Pro FWD cars with all their weight out in front of the front axle line.

Pretty sure he's mostly doing production fabrication these days coz companies are much more reliable to deal with than car guys. 

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  • 2 weeks later...

Hey man, @yoeddynzpointed me in the direction of your thread over on Retro Rides. What a read!

I was wondering if you might want to be a guinea pig for some of the stuff I'm working on around tuned length runners. It's got calcs and stuff, and I'm sure there's a graph or two that could be knocked up from it ;)

For a long time, I bought into the idea that inlet pressure waves were caused by air piling up against the back of the inlet valve as it closes and bouncing backwards and forwards along the inlet at the speed of sound until it reaches an open valve again. Apparently, according to the bods on Don Terrill's Speed Talk who are much smarter than I am, that's not how it works at all! (or, rather, that does happen but it's nowhere near being the dominant effect).

What actually happens is the piston creates a strong negative pressure wave as it reaches its point of fastest acceleration (usually somewhere around 84-90 degrees of crankshaft rotation). This propagates up the inlet until it reflects off the atmospheric pressure at the end of the inlet and returns as a positive pressure wave back towards the inlet.

What you want to do is size the inlet tract so that positive pressure wave arrives back at the tail end of the same stroke that created it, when the piston has slowed right down at BDC, or has even started coming back up the bore.

So far, so easy to calculate. The issue is that the atmospheric pressure the wave bounces off at the open end migrates down the runner a distance that's dependent on the strength of the negative pressure generated by the downward movement of the piston and the diameter of the runner. As this is the complicated stuff that programmes like Pipemax does and I haven't worked out yet, the best I can offer is to get into the rough ballpark for trial and error, with the possible suggestion that if it's not possible to fabricate a short enough runner, you can step up the runner diameter to make it appear shorter to the pressure wave.

I've made a little calculator so people can plug in their engine's specs and get a rough idea of what inlet lengths to aim for, and which ones to avoid. You'll need to know your target rpm, your stroke, your rod length, and your cam timings (actual measured cam timings, not advertised as they're often quoted in deliberately obfuscated or incorrect ways). Ideally your inlet temp would be useful too, but that's not too tricky to estimate.

It's a little crude at the moment as I've no idea how far the atmospheric pressure travels down the inlet, but it should give you a rough range to aim your inlet tract length to.

Would be dead interesting to compare the numbers the calculator spits out to the various different lengths of trumpet you've used. I think the only thing that would need to be measured is the length of the inlet tracts and the opening and closing times of your cams/valves (would need to be measured using a dial gauge and degree wheel, published specs are usually junk).

If I can work out how exhaust length tuning works then it'd be interesting to see how that matches up as well. The usual aim with exhaust runner lengths is to tune them for the trough caused by your tuned inlets so you get minimal reversion and a smoother torque curve. If one or other of your inlet or exhaust runner lengths are dictated by packaging then you could try and tune the length of the other one to compliment the length of the one you're restricted on...

Sorry for the wall of text! :D 

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Reminds me of a story from my old boss, building up a 2L Fiat twin cam race motor. He did all the math on cams intake and exhaust runners to get maximum power. His mate built the same engine with slap together parts and guess work.

Guess which was the better performer of the two?

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Not much to add since @Roman has it covered, Although a graph would be nice?    The few bendy runners ive used.  the centerline measurement seems to line up pretty well with a straight runner.  in regards to length tuning

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  • Roman changed the title to Romans 2005 Toyota Echo - Exhaust in progress / new big block setup

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