DIY Intake manifold. Pic heavy.

[Lemon S3]

I didn't fancy spending £500+ on an intake manifold, so decided to have a go at making my own.

Started off buying a 2nd hand AGU large port manifold on eBay.

Cut the top off

And straightened the top

Purchased 500mm of 120mm OD 3mm thick aluminium tube.

Cut two slots, tapered from one end to the other. This should, in theory, give equal flow to all four ports.

Then cut to length and shaped.

Offered up and trimmed manifold.

Cut, shaped and tacked on panels.

How the tapered slots look when in position.

Had a flange made up to suit TB with an o-ring groove instead of using a gasket.

Then made a cone to attach the flange to the plenum. This was pretty tricky without the proper bending tools but after a certain size disc was cut I somehow managed it with a hammer, a 2" bar and my trusty knee.

Everything was then finish welded together, with fittings for air temp sensor, breather pipes, DV and FPR.

Took it to our powder coaters and had it finished in crackle black which really makes it look smart in my opinion.
Also, had a little plaque made for it as well .

Excuse the rest of the tatty engine bay but all fitted looking lovely

I also had to shorten the fuel rail fixing points, using a milling machine as they're a lot higher than on the standard s3 manifold.

AGU manifold £15
120mm OD ally tube £20
Flange £80
Other materials "borrowed" from work.
Crackle black coating £50
Plaque £20

Not a bad manifold for just shy of £200, plus the added bonus of knowing I made it myself.

 

[badger5]

inlet manifold came out well.

 

[Madmax199]

The two slot idea is interesting to say the least, any reasoning for doing that? And is the plenum volume calculated or you went for the "it-is-what-it-is" approach? The finished product looks very nice!

 

[g60leigh]

Looks smart.

Interested how well it flows with the slots rather that port matched.


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[Rainbird]

Looks pretty decent. Have you been able to log anything in the way of pre/post-fitting differences?

 

[Stuart B]

I could have got you the plaque for £15

It looks like a nice unique addition - from a performance improvement point of view it would be good to see if it adds anything - at least you know it is nice and clean inside. as long as it doesn't make the car slower you are a winner

 

[Mav190sline]

Good effort mate. You should be well chuffed with that. Looks the business and "home made"

Well done

 

[badger5]

Looks smart.
View attachment 104327

Interested how well it flows with the slots rather that port matched.


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how it flows will never be known tho vs other/stock - bet there's more than one change being done at the same time.
neat fabrication tho.

 

[Lemon S3]

The slots are to equalise the plenum so all four ports get similar if not the same amount of flow.
The thing with doing it like this

the flow will rush past the ports, to an extent, hit the end of the plenum and most of it will go down the end port n the others will get slightly less flow than each other meaning the port next to the TB will get the least amount of flow and therefore run richer. I'm sure this can all be corrected in the mapping but why have the problem there in the first place.

I can't provide before and after flow rates as I've not only changed the inlet manifold. My theory/calculations can't actually be proved easily, so you'll just have to take my word for it

 

[Tj 0785]

Can you no just throw a standard one back on and measure the difference? It does look very well made

 

[Jeriho]

Make another one and send it my way i promise ill test it real good

 

[Chris90]

All that effort on a k04 turbo seriously isnt worth it. The stock item is more than capable to run a easy 450bhp if not more. By adding bigger inlets you end up loosing torque and just make more space to fill up with positive pressure when accelerating hard.

 

[badger5]

The Lehmann VW Motorsport inlet manifolds are dual plenum, with slot fill, and the one I had and measured years ago on badgerwagen the slot dimensions matched that of the throttle body cross sectional area (csa) - slot fill.

You may get more equal distribution of airflow in the cylinders but not more overall flow.

Well designed and FEA modelled taper plenum type manifolds, such as SEM and IE flow high and evenly also, without the need for dual plenum.

The works Lehmann cars were restrictor cars so the design of the plenum on them is part of running within those motorsport regs.. Quite different approach required in those.

The Dahlback Lehmann copy I had way back when....

 

[Lemon S3]

All that effort on a k04 turbo seriously isnt worth it. The stock item is more than capable to run a easy 450bhp if not more. By adding bigger inlets you end up loosing torque and just make more space to fill up with positive pressure when accelerating hard.

I agree, but it's not a standard setup. Aiming for 400+


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[Madmax199]

All that effort on a k04 turbo seriously isnt worth it. The stock item is more than capable to run a easy 450bhp if not more. By adding bigger inlets you end up loosing torque and just make more space to fill up with positive pressure when accelerating hard.

I disagree there (respectfully so), just because you're capable of running 450 bhp with something doesn't make it ideal. That 450 could have been 500 if you had a better intake manifold... staying hypothetical. It's like a 2.75" exhaust, you can make X power with it, but it's still a restriction and limiting you.

There is plenty of empirical tests and data proving this over the years, but this one is quite telling because it's an independent dyno test on a stockish 1.8t. (expect more gains at a higher tuned level).

http://www.superstreetonline.com/how-to/engine/1312-sem-motorsports-intake-manifold/

 

[superkarl]

I disagree there (respectfully so), just because you're capable of running 450 bhp with something doesn't make it ideal. That 450 could have been 500 if you had a better intake manifold... staying hypothetical. It's like a 2.75" exhaust, you can make X power with it, but it's still a restriction and limiting you.

There is plenty of empirical tests and data proving this over the years, but this one is quite telling because it's an independent dyno test on a stockish 1.8t. (expect more gains at a higher tuned level).

http://www.superstreetonline.com/how-to/engine/1312-sem-motorsports-intake-manifold/

I agree.
Lots of people say similar to Chris. For some reason people dont see it as worthwhile but the truth is i dont know of anybody thats tried it over here anyway. It may not yield amazing figures over an already highly strung setup, (£/hp very high) but its bound to offer the same performance for less work. And may alter the power delivery in such a way to be beneficial to some people.

 

[Madmax199]

I agree.
Lots of people say similar to Chris. For some reason people dont see it as worthwhile but the truth is i dont know of anybody thats tried it over here anyway. It may not yield amazing figures over an already highly strung setup, (£/hp very high) but its bound to offer the same performance for less work. And may alter the power delivery in such a way to be beneficial to some people.

Karl, the results of a good intake manifold is good at stock-like levels, but even better with a highly modified engine. I have even seen sizable gains even going from one aftermarket high flow intake manifold to another. One of the Unitronic guys did a test on his personal car switching from a 007SP unit to the highly praised SEM manifold. He gained substantial power even going from a high flow unit to a better high flow one.

Another good comparison test that I like to use is this one from Bill. I know it's a bit of an infomercial, but the bench flow tests and Dyno figures together are a nice way to help people visualize how it all works to make the power gains it does.

http://www.clubgti.com/showthread.php?171919-NEW-Highflow-1-8T-inlet-manifold-SEM-Manifold

 

[badger5]

infomercial indeed as back in 2008.... hehe, there was little available and I fancied seeing actual bench tests, so asked jp to do them. He was interested at the time also.. The results were shared. SEM on Badgerwagen ever since.

The gains from the link you posted Max are inmpressive.
Gains Made

+ 20.64 whp
+ 35.19 wtq
Before 187.73 whp and 208.23 wtq
After 208.37 whp and 243.42 wtq

I cant say I've seen that level of gains on that power level before myself however..

We have back to back tested SEM against IE one, and its pretty evens, with SEM slightly edging it, but IE having the reverse mount option the SEM not having. SEM ceasing production also.. Maybe all sold out already from the "last final batch"

 

[Chris90]

Gains are to be had, not saying There isn't... but also what losses are there. Torque... switchover with boost response between negative and positive pressures.

I've known a few well respected 1.8t mappers find this and even JP himself will say no real benefit of even small port vs big port until high bhp, as you loose the flow speed.

It's like the bigger throttle body, add too big and you loose partial throttle droveabilty and get poorer idle.

 

[Madmax199]

Gains are to be had, not saying There isn't... but also what losses are there. Torque... switchover with boost response between negative and positive pressures.

I've known a few well respected 1.8t mappers find this and even JP himself will say no real benefit of even small port vs big port until high bhp, as you loose the flow speed.

It's like the bigger throttle body, add too big and you loose partial throttle droveabilty and get poorer idle.

That's what we're trying to tell you, there are only gains! Just look at the independent dyno test in the article I linked. The TQ curve increased throughout -- and as a result, so did the HP curve (understandably since HP is nothing but TQ by speed).

I am not sure what else could be looked at if fishing for negatives. TQ, HP and flows gains throughout the rev range usually does the trick. No?

 

[<tuffty/>]

Dyno runs from when I did my manifold swap... actuator runs, no map change... large port head already, std cams, GT3071... swap was from std smallport S3 inlet to my fabricated large plenum AEB runnered inlet mani...

While there was a drop in torque right at the bottom it was pulled back after faffing with timing on a later mapping session...

<tuffty/>

 

[badger5]

Gains are to be had, not saying There isn't... but also what losses are there. Torque... switchover with boost response between negative and positive pressures.

I've known a few well respected 1.8t mappers find this and even JP himself will say no real benefit of even small port vs big port until high bhp, as you loose the flow speed.

It's like the bigger throttle body, add too big and you loose partial throttle droveabilty and get poorer idle.

Indeed. Not seen losses only gains.. Small gains on lower power cars (300bhp level) higher gains at higher power levels.

I don't see poorer part throttle on larger throttle cars, the drive by wire units are as good or as bad as you map them to be.. Pedal is just torque request, and throttle is programmable at the end of the day on ME7.5

If I was asked (I do get asked) would I buy a SEM, or IE inlet manifold when their build is k04 based, I would say no, put the money elsewhere for better gains.. My opinion. Both are largeport items.. Largeport is the "wrong head" to be using anyhow on small units, and in my experience sub 450bhp is adequate on smallport.. Very good port velocity and torque onset.. I'll dig out a comparison of GT3071 on stock AUM vs stroker GT35 on largeport to show the relative torque onsets. Its surprising (surprised me!)
Blue = stroker largeport GT35, Red = Stock smallport AUM GT3071 (cams)

at these relative boost levels

However, then add cams to stroker GT35 and some magic happened:
Green Stroker GT35, Yellow same car with cams, Red AUM GT3071

 

[Chris90]

Obvilously with a GT35, its a whole different game comparing it to something like a K04-023 or even a hybrid 023 IMHO. Some interesting data there though for the larger stuff.

Personally I have a 390bhp 1.8T (82mm pistons) running a TTE420 turbo and have no concerns with the inlet manifold restricting power. Currently running a large port setup/inlet and I would actually consider going back to a smaller port head and inlet if I was to do the build again.. (not that im going to spend all the money on doing so)

Be interesting to see plots of inlets being tested back to back on a K04 hybrid though. As you say, and dyno plots show, the small port is considerable better with delta power gains over the large port setup. Can even see the boost plot being far more earlier with the red trace on the small port.

Get your pressures across the head from the turbo as easily and as quickly as possible. Boost is only a measure of inefficiency

 

[Madmax199]

Obvilously with a GT35, its a whole different game comparing it to something like a K04-023 or even a hybrid 023 IMHO. Some interesting data there though for the larger stuff.

Personally I have a 390bhp 1.8T (82mm pistons) running a TTE420 turbo and have no concerns with the inlet manifold restricting power. Currently running a large port setup/inlet and I would actually consider going back to a smaller port head and inlet if I was to do the build again.. (not that im going to spend all the money on doing so)

Be interesting to see plots of inlets being tested back to back on a K04 hybrid though. As you say, and dyno plots show, the small port is considerable better with delta power gains over the large port setup. Can even see the boost plot being far more earlier with the red trace on the small port.

Get your pressures across the head from the turbo as easily and as quickly as possible. Boost is only a measure of inefficiency

Maybe you're overlooking this, but I don't know how this is not enough or evidence of gains on a stock frame turbo.

Gains Made

+ 20.64 whp
+ 35.19 wtq
Before 187.73 whp and 208.23 wtq
After 208.37 whp and 243.42 wtq

 

[Chris90]

Yeah, but them figures are easily achievable on a stock inlet so not really proving anything.

Thats like running a K300 (for example) at 300bhp wth flat boost profile, and adding a SEM intake and magically making a extra 20bhp at the wheels...If it was really that simple of bolting a inlet on to see them gains, then everyone would want one for a 1.8T. Jesus. If I saw a 25-30bhp (fly) or a 20whp/35wtq on my setup...id be bolting a inlet straight on... But unfortunately...doesnt work like that

 

[Madmax199]

Well, not going to pointlessly argue with you. I always had that theory that preconceived ideas can stop people from seeing evidence and data even when they're undeniably obvious. Feel what you want, have whatever opinion/theory you want to have, it's your right -- most people will go with the proven data!

 

[Chris90]

Look at the facts. Even bill at Badger 5 has never seen those gains at 225bhp before. Surely must tell you something. Its effectively saying the stock inlet is a restriction at 225bhp as it can no longer make power.

Im not arguine at all...im simply stating my experience of tuning these engines for about 8 years. Ive spoken with and seen work from the UKs top 20vt tuners over this time and they will all say the same.

 

[Madmax199]

Maybe it's selective reading, but didn't Bill himself posted in this very thread that he had only seen gains from higher flow inlet manifolds? Unless you don't count Bill as one of the top 1.8T UK tuners, what gives? Quoting Bill's statement below.

Indeed. Not seen losses only gains.. Small gains on lower power cars (300bhp level) higher gains at higher power levels.

Saying you have been tuning the 1.8t for 8 years and have seen/talked to top UK tuners doesn't validate a point. That's like me saying that because I have broken K04 and K04 hybrid known power records, and have been around top US tuners that my opinion can refute presented facts. BTW, I can present several other dyno comparisons, but what's the point if opinions and who we've been around is what validates our arguments.

 

[Chris90]

Maybe the car in testing had a leaky PCV valve or boost leak under the inlet and replacing it cured it? Any other data to prove?

If the likes of R-tech dont see any gains that are worthwhile...would you believe their independent advice?

Surely a larger manifold with a better Volumetric Efficiency would show there as being gains more at the top end of the power band where the OEM/standard one was struggling to cope with power? Rather than a gain right across the board.

NObody doubts a bigger inlet wont make power....Just its not going to make 25bhp and 40lbft (fly) on a near standard engine.

Jeez, thats a k03s judging by the yellow golf in the pictures. Do you not think a tiny turbo would take longer to spool up therefore power would be shifted right in the plot? Chances are, they fixed a underlying issue in the plot and thats where your gain is coming from IMHO.

 

[<tuffty/>]

The OP's car is an S3

<tuffty/>

 

[Chris90]

I know. The data that madmax was showing was for a golf with what looks like a AUM lump

 

[superkarl]

I know. The data that madmax was showing was for a golf with what looks like a AUM lump

Which only further proves the point everyone is trying to make

 

[Chris90]

So you are saying the stock manifold is a restriction at ~200bhp?

At what bhp level do you believe the standard inlet starts to choke and becomes inefficient?

 

[badger5]

the point which max is making and the USA Golf dyno plots suggest is there are gains to be had....... The level/qty of gains to be had is variable as are all things dynoplot related, but has previously stated, never seen losses, only gains, but I personally haven't seen the US golf's magnitude of gains on baby turbo.

Getting hung up on "restriction", and talking "deltas" makes me LOL - straight out of your fave tuners mouth.

Efficiency gains is what makes for more power... The only thing likely to choke on an otherwise stock small turbo car is on its own turbo.. Its tiny.

Big turbos are a different ball game.

 

[Prawn]

Chris, you're failing to distinguish between restrictions and efficiency here, and they're 2 very different things.

Let's take a ko4 car for example, and talk UK numbers (sorry max)

We all know a ko4 can make 300bhp on a good car with a stock inlet - the inlet is not restricting it.

So, for arguments let's detune said car to 250bhp.

Add a high flow inlet at that 250bhp tune, and you will see gains across the board. Perhaps not huge gains, but gains all the same.

This isn't because the stock inlet was a restriction, but simply because the high flow is more efficient.

Karl summed it up in his first comment nicely. Even if peak figures don't show huge gains, the same output can be achieved for less work through increased efficiency.


I think hypothesising that a vac leak was fixed during the manifold swap is perhaps a little desperate in terms of trying to disprove results.

This was 2008 remember, a time when 220bhp from a ko3s was considered exceptional.

 

[superkarl]

There is probably a drop in boost with increased efficiency also, same duty cycles, so perhaps more gains to be had when turned up to the same boost levels. Something i don't think the comparisons mention, tufftys comparison is actuator pressure so is fixed. This may account for the significant gains in power.

 

[Chris90]

The would be a drop in boost with increased efficiency.

You play around with the vvt timing and timing between cams and crank and can see a big drop in boost pressure. I've seen drops of 3 psi.

 

[Madmax199]

The would be a drop in boost with increased efficiency.

You play around with the vvt timing and timing between cams and crank and can see a big drop in boost pressure. I've seen drops of 3 psi.

Now that everyone (including a top UK tuner) is telling you the same thing, I'm assuming we can get past the "restriction and choke" point you were focusing on instead of seeing the obvious increased efficiency?

 

[badger5]

fixating on boost is daft. Flow you want.
vvt at inappropriate moment will show more plenum boost pressure but not for more torque - ie Wrong.

 

[Chris90]

Would Be good if some of the top tuners understood choke though, Not just winding boost up for no more power. Seen it numerous times, such as the image below... clear choke point in higher rom. Identical torque and power but yet a 6 psi boost increase. What caused that?


Actually half interested to buy a SEM inlet and see if there is any difference straight back to back with comprehensive data from the Ecu