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extra lag with aftermarket intake manifold?


msupra1
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I am making 900bhp through a BW 66mm turbo.

10:1 compression, pretty responsive setup I would say.

 

Doing a couple changes to my setup, and one of the things I'd love to add is an aftermarket intake manifold.

I just love the way they look and hoping to gain some more power with one.

 

I am looking into something such as Greddy. Do they add any additional lag? I've read that as long as its not a cheap ebay manifold and a quality piece, it should only have positives to this mod?

One thing I am trying to avoid is adding additional lag. I get full boost around 4400rpm and redline is 8500. Love the current power band.

 

Cheers

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  • 3 months later...

Just wanted to bump this thread and see if anyone else have any experiences from upgrading their intake manifold or have knowledge on it

 

Again from my understanding there should be some 'minor' low end losses but hoping this wont affect the way the turbo spools.

 

Getting ready to buy one but don't want to be disappointed with the affects on the low end (if it happen to be bad)

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I doubt they would add any extra lag at all, the volume change is minimal in terms of air flow volume. What i would be concerned about is how equally they flow air to all ports, something the stock manifold *WILL* have addressed, but possibly not with aftermarket.

 

Chris, have you any experience with twin chamber plenums? The audi 5 cylinder guys rave about them, but I'm yet to see them being adopted by Japanese car tuners.

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I'd ditch an aftermarket manifold in favour of opening up a factory intake and porting it. That's what was done on mine.

 

Thing is, the stock setup was a compromise for the sake of packaging, there are good, proven gains to be had with a decent plenum. But it generally means relocating the battery, which is a pita if you value your boot space (although I suppose one of those smaller li batteries might go in one of the rear wings)

 

I've always loved the vielside plenum, shame they're so rare :(

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Thing is, the stock setup was a compromise for the sake of packaging, there are good, proven gains to be had with a decent plenum. But it generally means relocating the battery, which is a pita if you value your boot space (although I suppose one of those smaller li batteries might go in one of the rear wings)

 

I've always loved the vielside plenum, shame they're so rare :(

I have the battery relocation to boot and have kept all the space with a slimline battery after having the SRD Greddy style manifold installed. There are definitely gains to be had by upgrading to a reputable make.

 

 

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500rpm of spool is a lot!

See that's what I'm afraid of.

 

I am thinking to maybe stick with the stock intake and clean it up by shaving the throttle body clean and removing anything from it that's not necessary.

 

Keep it simple. I'd modify your stock intake and retain the factory fit. No battery, fuse box or pas reservoir relocations or cutting holes in your car.

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If you look at the linked build thread by DanDan I think he covers some info about the modified stock manifold.

 

http://www.mkivsupra.net/vbb/showthread.php?194439-Dan-s-Supra-Project/page12&highlight=Alcon+brakes

 

The next page on the above link has pictures of the inside of the manifold.

Edited by mwilkinson (see edit history)
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The plenum on a FI engine just flows air. It has to merely allow an equa flow both under N/A and boosted conditions with no substantial pressure drop. Where things become critical is in the ports, where a fuel wetted, far denser air has to flow without fuel separation, hence attention to surface finish and port shapes. The stock plenum *WILL* have been *PROPERLY* flow tested, both as a CAD and in use on a real engine. The aftermarket ones? Who the hell knows...

 

Do you need an aftermarket one?

 

A: I like the looks, they look the business, I don't care if the work better or worse than stock. You need one...

 

B: I'd buy one if it improved power. Two ten quid pressure / vacuum meters off Ebay will tell you. One pre the throttle body, one on the plenum. If you see the one pre reading substantially higher thasn the one post the TB at peak torque or peak power RPM under boost, then you might benefit from a bigger bore TB. Too big though and throttle progression will go to pot, with the first bit of accelerator movement going from idle to full power, the rest doing nothing. You might even get a bad combination of too big a TB and a bad plenum design where lifting OFF the throttle a tad the engine makes more power. Disconcerting and a sure sign of the combo being wrong. Have I seen this on 2JZ-GTE's? Hell, sure, several times. You may need one, you need to test...

 

 

Does a bigger diameter TB or bigger volume plenum add turbo lag? Unlikely, the sheer volume of air being moved in cubic feet is so huge it makes IC pipe volume and plenum volume only a tiny percentage of what the turbo puffs out under boost. I have never perceived an increase in lag due solely to a bigger volume plenum. But a bad plenum that gives uneven air distribution to the ports is bad, for sure. If one port gets more than its share of air that has to be run richer somehow. Short of measuring AFR on a cylinder per cylinder level all you end up doing is richening or weakening to get an overall correct AFR, and the ports that receive different amounts of air to the others may be running their cylinders rich or lean, and you won't know.

Edited by Chris Wilson (see edit history)
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The N/A Supra engine already has one.... ;)

 

It's not a twin chamber as they are used in forced induction.

 

A twin chamber intake manifold has a thin opening along side the whole manifold which creates an even flow to all intake ports.

 

image

image

 

They are usually used in WRC rally cars IMSA cars etc..

 

image

 

 

You can buy a DIY kit from here:

http://www.amwdynoservice.com/page25.php?view=productListPage&category=14

 

It's the same as in the Instagram photo I posted above.

Edited by Krister (see edit history)
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The Skoda plenum, for example, is designed to equalize air flow across all 4 cylinders under boost. the high velocity air will not favour changing direction into the first two ports, so the cross sectional area of the plenum is increased to lower air velocity. They spend weeks on dynos sacrificing dozens of engines getting all this right, and WRC cars are a bit "odd" in having a turbo restrictor, so they run relatively low RPM and try and maximize torque. Another reason for elaborate intake designs. Dual plenums with a solenoid valve to vary its volume like on an N/A Supra are all about pulling up peak torque at a favoured RPM band. Here#s the plenum I did for my 4AGE turbo engine, to similarly try to even air flow from its single TB

DSC08748.jpg

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