GSlender's Track Beeotch!

[rascal]

The airbox inlet is 76mm which is almost 1.7 times the individual 45mm TB inlets. Both pipercross and jenvey airboxes are also 76mm so I figured that must be good enough - besides you'd think they would know!G

However its the cross sectional area that you are dealing with, so 4 x 45mm inlets (6360mm2) can flow 40% greater than what 1x76mm inlet (4536mm2) can so you will be choking it down by fitting a single 76mm vs the 4 x 45mm ones.
You'd actually need an inlet of 90mm to flow as much air as the 4x45s are capable of, at constant WOT.

[gslender]

However its the cross sectional area that you are dealing with, so 4 x 45mm inlets (6360mm2) can flow 40% greater than what 1x76mm inlet (4536mm2) can so you will be choking it down by fitting a single 76mm vs the 4 x 45mm ones.
You'd actually need an inlet of 90mm to flow as much air as the 4x45s are capable of, at constant WOT.

Only if the engine was a 1 stroke!

G

[rascal]

Only if the engine was a 1 stroke!G

hmm, I understand your point, though that would suggest that a single 45mm inlet would be sufficient to feed the 4x ITBs.
That's even smaller than the standard factory throttle body which definitely limits flow on higher hp motors and the reason many go for itbs.. (or is it the port size on the inlet manifold that is the limiting factor?)

[sailaholic]

Car is packed up for the dirt sprints tomorrow. For memory the smallest section is where the inlet pipe merges to the airbox. Which is a bit hard to measure but I'll see what I can manage.

I just had a thought, to test the filter / vs air box theory I can just take it for a drive with out the filter on it.

G, always welcome to come and eyeball it if you want. Even have a drive if you want.




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[speed]

Wow, so clean, tidy and organised. Do you still have the supercharged 5?


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[gslender]

hmm, I understand your point, though that would suggest that a single 45mm inlet would be sufficient to feed the 4x ITBs.
That's even smaller than the standard factory throttle body which definitely limits flow on higher hp motors and the reason many go for itbs.. (or is it the port size on the inlet manifold that is the limiting factor?)

well no.... the stock 1.8 engine has a 63mm intake throttle and pipework. it has been proven that this size isn't a restriction until nearly 8000rpm or above, so there is no need to have more than that from an airflow perspective. any bigger and you start to reduce throttle response at low rpms on a single TB system like the OEM manifold/intake.

i've built an airbox with a 76mm intake pipe and 45mm individual throttles so I get the great throttle response (as they are sized to suit the engine) and my airbox is large enough to flow for a 2.0L engine at full song of 9,000rpm !!!

so yep, pretty sure the airbox isn't going to restrict the ITBs... but happy to have someone point out the errors in my thinking.

G

[gslender]

Wow, so clean, tidy and organised. Do you still have the supercharged 5?

nope. sold the kit about 12 months ago....

[sailaholic]

I think your thinking is on track G, it's the filter element itself that I think will be a restrictor

[gslender]

I think your thinking is on track G, it's the filter element itself that I think will be a restrictor

Ahh, but you don't think that 4 socks designed to support a 45mm ITB would flow/restrict equally as a filter designed for a bigger 76mm intake?

Isn't the the solution to just install any 3" (76mm) hi-flow air filter then? Geez, I could go and find a 4" filter and reducer and surely that'd be ok !?

[sailaholic]

I know the individual filter socks are a restriction on flow based on the testing by my tuner. But this is more to do with limiting a nice flow pattern that the trumpet is designed to produce

There is data for the flow of various filters per unit of surface area. After that yes if agree it's just a case of getting a big enough filter area.

When I did my dodgy swap I just used the same filter as I had used in a single trumpet. If your filter is different then it may be big enough.

[gslender]

Just had the Fulcrum boys do the alignment on the car - ready for Monday week.

Fronts set to 0 toe, 1.5 deg neg camber with 6.5 deg caster

Rears set to 0.5mm toe-in, 1.7 deg neg camber

Nice!

[Magpie]

I'm running 2° of caster and the car is very nervous on normal streets, it will be interesting at time attack tomorrow.

Why did you go for more rear camber?

[gslender]

Max caster is always the way after you've dialed in the camber. Caster makes you faster.

Not sure I'd agree that .2 of more rear to front camber is that noticeable, but the consideration is that with stock sway bar it'll probably move and lean more in the rear than the front which has got an upgraded sway.

Like most things, I'll go around the track, decide what's not working, and go back and adjust for the next outing. Most of the recommended track specs suggest more rear than front... so why not!?

G

[gslender]

Legendary lanny alignment specs...

http://www.hummingbirds.net/alignment.html

[Magpie]

I'll raise you a 949 spec

Front camber: -3.5° (or as close as you can get to it)
Caster: >+4.5° or max available once you reach camber targets
Front total toe: 0

Rear camber : -3.0°
Rear total toe: +1/16~1/8"