Trumpets inside factory plenum 4age 20v BT

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Trumpets inside factory plenum 4age 20v BT

Postby ae111 corolla gt » Sat May 27, 2017 7:33 pm

Hey guys,

Still kinda new to 4age's. I've got a few questions that I couldn't really find an answer to, and these are as follows:

1. I've heard that 50mm trumpets are the largest length trumpets that can be fitted in the factory airbox, is this true? And if so, is the torque in the bottom reasonable because its still inside the plenum? I know that 50mm trumpets result in average power and torque in the low RPM without the plenum, but haven't seen many results of them in the plenum.

2. My second question is can you fit longer trumpets in the bigger part of the airbox? For example, cylinder 1 and 4 have 50mm trumpets, and the two middle ones have 90mm trumpets maybe? Is that a good idea? Theoretically sounds kinda alright, because 2 cylinders will provide more lower end torque, and the other two for higher end, and I've heard some people say long trumpets are good for both low and high end power. But I don't know if this is a good idea, so if someone could elaborate more on this, that would be good. Thanks
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Re: Trumpets inside factory plenum 4age 20v BT

Postby jondee86 » Sun May 28, 2017 1:17 pm

I like the idea... it's different and it looks cool :)

Image

And apparently some serious motorcycle manufacturers like it too.

Cheers... jondee86
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Re: Trumpets inside factory plenum 4age 20v BT

Postby ae111 corolla gt » Sun May 28, 2017 2:08 pm

jondee86 wrote:I like the idea... it's different and it looks cool :)

Image

And apparently some serious motorcycle manufacturers like it too.

Cheers... jondee86


Yeah it's different and I guess someone has to do it cause I haven't seen many people do it, apart from motorbikes and some V8's. Hopefully I can fit 75mm for cylinder 2 and 3. I think think 80-90mm would be pushing it in terms of space. Might event have to modify the factory plenum a bit. Should be good though!
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Re: Trumpets inside factory plenum 4age 20v BT

Postby Vertigo » Sun May 28, 2017 5:37 pm

It would probably flatten your torque curve a little.

A better idea, if made of money, would be a variable length runner.

https://www.youtube.com/watch?v=JMVioC2XGO0
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Re: Trumpets inside factory plenum 4age 20v BT

Postby ae111 corolla gt » Sun May 28, 2017 6:37 pm

Vertigo wrote:It would probably flatten your torque curve a little.

A better idea, if made of money, would be a variable length runner.

https://www.youtube.com/watch?v=JMVioC2XGO0


What would be the reasoning behind a flattened torque curve?

Also would I lose a significant amount of torque if I ran 50mm trumpets in the plenum?

In terms of the variable length stuff, that would probably be way out of my budget haha
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Re: Trumpets inside factory plenum 4age 20v BT

Postby Vertigo » Sun May 28, 2017 9:11 pm

A flat curve is great, IMO!
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Re: Trumpets inside factory plenum 4age 20v BT

Postby ae111 corolla gt » Sun May 28, 2017 9:12 pm

Vertigo wrote:A flat curve is great, IMO!


Oh thats awesome haha. Makes sense when you think about it as well. Thanks for that!
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Re: Trumpets inside factory plenum 4age 20v BT

Postby jondee86 » Tue May 30, 2017 12:04 am

ae111 corolla gt wrote:I've heard some people say long trumpets are good for both low and high end power.

The complicated theory for calculating the optimum length of intake trumpets involves
such parameters as the overall length from valve head to open end, diameter, velocity
and at what rpm the ram effect should peak. The simplified theory just says 110mm long
trumpets work best on 20V 4AGE's :)

And that may well be true for engines with the OEM intake manifold and ITB's. The Toyota
factory engineers (who of course know fcuk all about intake design) went to a lot of trouble
to come up with a trumpet that kept noise down, preserved a bit of low end torque, and
could fit inside an airbox with some decent volume. Not to mention a cold air intake and
a filter that actually keeps all the wear particles out of the engine.

[RANT] Fortunately, it is easy enough to fix the factory fcukup by ripping all that shit out
of the engine bay and whacking on some Trademe trumpets with wire mesh screens on the
end. Now you have a race engine that sounds like someone strangling a Turkey when you
give it a bootfull outside the netball courts on a Saturday afternoon... bewdy aye :)

Truth is you just lost some power, your engine doesn't idle too good, bogs in the midrange
and sounds like a Honda... stink aye :( When you get tired of all that (and it won't take long),
you might get lucky and be able to find all the shit you ripped out and put it back. [/RANT]

So the point that I'm trying to make is that trumpets are tuned to have a pressure wave
arriving at the inlet valve at the correct moment to creat a ramming effect that helps get
a bit more charge into the combustion chamber. More charge equals more power. However,
the ram effect peaks at certain frequencies, and you have to choose the rpm range band
where you want to get that extra power... for example 5000 to 6000rpm. When the physical
dimensions of the intake tract are fixed, the only variable you have available for tuning the
ram effect is trumpet length.

Can it work at both high and low rpm ? For a fixed length trumpet the simple answer is NO.
You tune for the strongest ram effect to occur at where you want peak power. There are
weaker harmonics that occur in other (lower) rpm ranges, but their effect would be negligible.
There are some on-line calculators that predict the best length for trumpets under a known
set of conditions. For your experiment with two different lengths of trumpet, you should
try to select lengths that work in overlapping bands... for example 4-5000 and 5-6000rpm.

And when fitting trumpets inside the factory airbox, you will need to keep at least 20mm
clearance between the end of the trumpet and the airbox wall. Better if the wall is angled
as that will help prevent reflected pressure waves from interfering with the tuned wave.

Good luck !!

Cheers... jondee86
1984 AE86 Corolla GT Liftback, NZ new... now with GZE
spec small port, twinscrew s/c and water/methanol injection :)

Watch this space >>> <<<
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Re: Trumpets inside factory plenum 4age 20v BT

Postby ae111 corolla gt » Tue May 30, 2017 2:08 am

jondee86 wrote:
ae111 corolla gt wrote:I've heard some people say long trumpets are good for both low and high end power.

The complicated theory for calculating the optimum length of intake trumpets involves
such parameters as the overall length from valve head to open end, diameter, velocity
and at what rpm the ram effect should peak. The simplified theory just says 110mm long
trumpets work best on 20V 4AGE's :)

And that may well be true for engines with the OEM intake manifold and ITB's. The Toyota
factory engineers (who of course know fcuk all about intake design) went to a lot of trouble
to come up with a trumpet that kept noise down, preserved a bit of low end torque, and
could fit inside an airbox with some decent volume. Not to mention a cold air intake and
a filter that actually keeps all the wear particles out of the engine.

[RANT] Fortunately, it is easy enough to fix the factory fcukup by ripping all that shit out
of the engine bay and whacking on some Trademe trumpets with wire mesh screens on the
end. Now you have a race engine that sounds like someone strangling a Turkey when you
give it a bootfull outside the netball courts on a Saturday afternoon... bewdy aye :)

Truth is you just lost some power, your engine doesn't idle too good, bogs in the midrange
and sounds like a Honda... stink aye :( When you get tired of all that (and it won't take long),
you might get lucky and be able to find all the shit you ripped out and put it back. [/RANT]

So the point that I'm trying to make is that trumpets are tuned to have a pressure wave
arriving at the inlet valve at the correct moment to creat a ramming effect that helps get
a bit more charge into the combustion chamber. More charge equals more power. However,
the ram effect peaks at certain frequencies, and you have to choose the rpm range band
where you want to get that extra power... for example 5000 to 6000rpm. When the physical
dimensions of the intake tract are fixed, the only variable you have available for tuning the
ram effect is trumpet length.

Can it work at both high and low rpm ? For a fixed length trumpet the simple answer is NO.
You tune for the strongest ram effect to occur at where you want peak power. There are
weaker harmonics that occur in other (lower) rpm ranges, but their effect would be negligible.
There are some on-line calculators that predict the best length for trumpets under a known
set of conditions. For your experiment with two different lengths of trumpet, you should
try to select lengths that work in overlapping bands... for example 4-5000 and 5-6000rpm.

And when fitting trumpets inside the factory airbox, you will need to keep at least 20mm
clearance between the end of the trumpet and the airbox wall. Better if the wall is angled
as that will help prevent reflected pressure waves from interfering with the tuned wave.

Good luck !!

Cheers... jondee86


Wow thanks for that!

In terms of running different length trumpets, I contacted SQ engineering and they said it's a real bad idea unless you have individual cylinder tuning which I obviously don't have. And the reason why it's bad is because it cylinder is tuned under the assumption that all cylinders are working the same, and if the trumpets are different, some will breathe better at various different rev points and this can cause detonation or leaning out of the mixture. So I think I'll be settling for some good quality SQ engineering 50mm ones to fit inside the factory plenum, because according to them, their customers haven't reported on any loss of power in the lower RPM, instead they've noted increase in the mid range and top end, so that's good! And it also keeps everything looking stock as well, which is good.

Thanks again for your detailed description!
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Re: Trumpets inside factory plenum 4age 20v BT

Postby jondee86 » Tue May 30, 2017 2:34 pm

Most things in life involve some kind of compromise, and trumpets are no exception.
The factory has to design their trumpets to meet a lot of criteria other than maximum
performance. They can't trade off driveability, noise reduction space requirements just
to gain a couple of extra kW at 8000rpm. Mr and Mrs Joe Average don't spend a lot of
time at 8000rpm, but they do drive around town a lot, and expect their car to be quiet,
smooth and reliable.

So while I think your idea is interesting, unless you are prepared to put a lot of effort
into testing and analyising results, better to go with the 4 x 50mm trumpets and spend
your time looking for improvements in other areas.

Cheers... jondee86
1984 AE86 Corolla GT Liftback, NZ new... now with GZE
spec small port, twinscrew s/c and water/methanol injection :)

Watch this space >>> <<<
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Re: Trumpets inside factory plenum 4age 20v BT

Postby ae111 corolla gt » Tue May 30, 2017 3:27 pm

Yes that's very true!

50mm trumpets should be all good I think, and should work well with my Tanabe exhaust. I'll report on the results once I buy them. Cheers for your input!
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Re: Trumpets inside factory plenum 4age 20v BT

Postby Vertigo » Tue May 30, 2017 6:56 pm

Dont forget, the head is where the power is made. Port it and cam it, if you are serious about power.

Or turbo.
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Re: Trumpets inside factory plenum 4age 20v BT

Postby ae111 corolla gt » Tue May 30, 2017 8:28 pm

Vertigo wrote:Dont forget, the head is where the power is made. Port it and cam it, if you are serious about power.

Or turbo.


Yeah that's true, but won't be able to afford that cause I'm still a student. Dunno if it would be worth it to be honest, those mods can cost a lot but for only 15-20kw maybe. Would rather save for a JZX or something haha
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Re: Trumpets inside factory plenum 4age 20v BT

Postby Vertigo » Wed May 31, 2017 9:05 am

Fact is though that the blacktop 20v is in a very high state of tune to begin with. Its going to cost money to get it pushing more power.
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Re: Trumpets inside factory plenum 4age 20v BT

Postby Lith » Wed May 31, 2017 12:20 pm

Have a look at Mark's thread... 70mm SQ Engineering throttles in a modified stock plenum, seems to work well

http://forums.toyspeed.org.nz/viewtopic.php?p=956382#p956382
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Re: Trumpets inside factory plenum 4age 20v BT

Postby Flannelman » Tue Jul 04, 2017 8:11 pm

Second that Lith. I found on my Silvertop that making a bigger plenum helped filling the mid-range dip with an extra 3kW from 5800-7800rpm.

Image

Still standard ECU and trumpets.
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Re: Trumpets inside factory plenum 4age 20v BT

Postby 1I1 » Fri Jul 07, 2017 10:52 am

Flannelman wrote:Second that Lith. I found on my Silvertop that making a bigger plenum helped filling the mid-range dip with an extra 3kW from 5800-7800rpm.


Bare in mind the modified plenum on mine was only to allow fitment around No1 cylinder velocity stack. iirc without plenum there wasn't any dips - I just prefer the idea of not running open TB's to keep debris out of the motor as I'm bound to find the gravel traps one day.
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