20 valve trumpets: silver vs black

[roadsailing]

I have been looking at some blacktop trumpets recently, and found some of the differences from slivertop ones marginally interesting, so stick you Toyota anorak on and read on!

From my rough measurement, the silvertop equivalent straight length is 170mm, the blacktop is 140mm.

Silvertop trumpets are made out of glass filled nylon in two pieces, which are then badly ultrasonic welded together, resulting in mismatching joins and a shitty internal surface.

Blacktop trumpets are one piece moulded from some kind of rubber, you can readily bend them, i'd guess toyota did this to reduce noise and probably cost.

Both types have a fairly shitty small lead in at the open end, but the blacktop looks slightly better.

Bolt holes on the blacktop are about 10mm further apart from each other than the silvertop ones.

here are some photos, the black trumpet is the rubber blacktop one, the red one is on of the two types found on each silvertop, blacktop uses 4 trumpets of the smae design.

here are some photos, the black one is the blacktop

[gixer]

Imec vs blacktop



Running these ram tubes back to back on dyno INSIDE factory airbox, netted an EXTRA 3kw below 4200rpm and an extra 6kw above 4900rpm!!!

[roadsailing]

shit really? did they lose power anywhere? did you have to re-tune? i heard a claim from someone that they had never seen a power gain running alternate trumpets.

[gixer]

I did back to back on same dyno. gain down low was not expected! between 4200rpm and 4900rpm the dyno curves were the same(exactly ontop of one another, we can overlay runs), with the imec ram tubes there were no losses!!
When it hit's 4900rpm it basically picks up those 6kw's straight away so on the road there is a very noticable kick in acceleration compared to the standard tubes. Above 4900rpm the power curve is basically lifted 6kw upwards everywhere(if that makes sense?) till redline. On road is very annoying to drive as it peaks power at the rev limiter(has it dropped...who knows..damn limiter, and still pulling hard), needs more rpm....9000rpm maybe!

[Sam_Q]

that is interesting, do you mind if I use your pic and info to add to a guide I wrote?

http://www.ae86drivingclub.com.au/fa...age/20vengines

[kassma]

Hey Roadsailing...

Was just wondering where you purchased your IMEC Velocity stacks, as I'm looking at getting one set for my AW11 which is running a BT 20v engine.

Thanks
MIKE.

[gixer]

The best place to get them outside of Japan, is Pass racing in the states, unfortunately with the crap dollar they cost more....but they are sweetly made

[rick q]

Another local place worth looking at is JNT Performance ( http://www.jntperformance.com.au/ ) , though you'll have to make up your own flanges.

No connection - just a satisfied customer

[-GT-]

Gixer, are you able to give us some specs on the IMEC ones? Length in particular, and if possible an idea on taper (or max and min IDs to compare to length)?

I'm guessing they're shorter than factory if they're straight and still fit in the factory airbox, interesting that you didn't lose power anywhere - is this with a programmable ecu on the engine, and was it re-tuned before the 'after' figure?

[gixer]

I didn't take any measurements before fitting but did take lots of pics. I went to get printouts off dyno today and hard drive crashed so won't be to next week when IT put in new HD. This mod was performed on a low km stock AE111 Levin.

First run I did netted 90kw, I then changed all fluids(running Royal purple in engine/ MTL redline in trans axle) new plugs, air filter, fuel filter, reset timing etc, netted 94kw, then fitted I.mec ramtubes netted 100kw.

I.mec are actually Porsche tuners, but they did do a few N1 parts for AE111....go figure!

they are fairly short, around 35mm from memory with a very large radius into a very large diameter bellmouth. Before the HD crashed today I actually got the first run and last run overlayed and you can see the improvement down low(about 3kw) then the improvement up top(about 6kw)

[oldcorollas]

is there a drop when you run the short trumpets and remove the airbox?

[gixer]

stock vs I.mec


[URL=http://g.imageshack.us/img18/imec003.jpg/1/][IMG]http://img18.imageshack.us/img18




NOTE THEY ARE IN STD AIRBOX, NO AIRBOX = LOSS DOWN LOW

[gixer]

Stewart, yeah with no air box it lost out quite a bit.

the overlaid curves are interesting in that the I.mec's produce more down low THEN run with the std curve for around 700rpm(from memory) then pull away, they basically pull away 6kw straight away, on the road the extra 6kw is very noticable.

[gixer]

Also even tho they are in stock airbox etc, induction noise is much louder, I ran a silver 20v in my ae86 for about 10years(can't remember exactly too long ago and I'm old now!) but the original ram tubes are also shaped to disipate noise, everytime the intake sound wave changes direction it loses energy.

When the stock tubes were fitted, the best way to describe the intake noise was like a vtec type sound, with the i.mec's it's like BRAHHHHHH, much noisier.

[gixer]

As a side note, fucking with ram tube lengths has been a hobby of mine for years, when I originally had my first silver 20v on the engine dyno, I tried numerous different lengths, just by changing lengths netted an extra 11bhp at the flywheel.

Also I own a bike built by Honda for World superbike homologation, it has many many HRC race parts on it, it's a V4 engine, I run HRC ram tubes in an HRC airbox, the rear of the air box tapers towards the back of the fueltank. The front HRC ramtubes are 20mm and the rears 40mm, they are loading(soundwave) the ramtube against the airbox lid.