Custom inlet manifold.
 

Over Christmas I have quite a bit of time to myself so decided to make my own inlet manifold with the different bends and sheet ally I have. It will be purely for looks but I still want the car to run nice and (maybe better than standard if possible)- but not needed..

So my questions would be if I built some sort of trumpets into a plenum would this sound as well as run okay? Also is it worth keeping the internal volume of the plenum and throats the same as standard?

Any help would be great it's more of a project to learn than anything else but it would be a nice show piece at the same time...

runner length etc plays a big role

but spec and engine will be a good starting point

See this is why I want to lean more about this sorta stuff. Engine is pretty much standard. It's a mk1 45kmiles vtr engine with a raceland 4-2-1 manifold lightened fly balanced on the crank, lightened aux pully.

That's pretty much it.

I'm not looking for more power out of this just for the car to run nice and idle nice its more a learning experience.

I have built my own inlet manifold for a b16 Honda engine but I worked from a plan using stainless tubes and flanges made in a kit by golden eagle.

best person to ask would be sandy

or do some googling on inlet tract length etc

this is a good read

http://www.team-integra.net/forum/bl...culations.html

Spot on mate ill have a read of that.

I didn't really want to ask sandy as i think he would be in the same boat as people asking me how i get the finishes i get at work ect.

As said anything i can learn from it will be a bonus because tbh I am sick of fitting shite that people have bought on ebay thinking "well I can make that but it should be better."

i was thinking that while i was writing it tbh lol

kind of defeats the purpose of his job

but theres plenty info out there

Look through google scholar. You'll find tons of papers on inlet design. Depending on how refined you want it will depend on how dig you need to research, but the digging is endless.

I've probably got photos somewhere of the innards of a Dp inlet if that helps at all? I'll try and keep an eye on this thread if you want em.

That would be good mate I got a basic formula for what length I need. Just got my head full of it all at the mo..

Inside of the manifold I made, with internal trumpets.

Here's a photo of Deans DP inlet when he had it cut about.



And here's mine:









Hope they help :)

Inlet design really is an art... In America certain companies spend an absolute fortune designing single tb inlet manifold and some have got that good that theyre pretty much as good as ITB's. I know the design I'd go for if I had to start from scratch but is quite difficult because the way these engines are layed out.

First of all you need to decide what the engine consists of I.e charged, cams, head etc

will a C2 vts inlet fit? as that'll flow a good 180 very nicely.

As I said I'm not bothered about power figures as long as I learn something from it.

That DP manifold is a nice looking bit of kit!

It's an off the shelf solution to a problem/need. If I were starting again, I'd probably still run this inlet but with a smaller throttle body. 70mm is much too big even at high power. the fuel rail should have welded fittings not the bolt on ones they supply. The supplied throttle body is a jap/generic ebay special, and the welds on the manifold are a little cold in places but it's not too bad. Still - I'm not sure you should be able to pick faults like this in a £1000 manifold.

If there was a market for them, someone could make money designing something similar and selling at a much lower cost.

The dp exhaust manifold can suck donkey dick though. Never seen a straight one from the factory, and again, not something I want to repair before fitting...

Exactly why I'm not buying a turbo mani from em and trying my own if it warps I'm not fussed won't cost me 700 so can try a few :)

Danny made an excellent manifold himself. He might give you some guidance :) constella would also be able to make one - they made their own 205 Evo manifold.

im trying a ramhorn style one like all the civic/starlet folk seem to run

The DP Engineering inlet manifold is very well made really. But It price will be ... but it worths at all! I'm looking too after an aftermarket inlet manifold too so I think to contact DP soon and will post some info after that.

Dp manifolds are cheap compared to some gear...
Don't know why more people don't run nortech manifold, cheaper, based in the uk and will make anything you want!
Oh an you won't have hassles like with the dp stuff.

Do they currently make one?

Ross, was the dp mani an improvement? What were you using before?

Hey dude! Can you post us some links of nortech intake manifolds for saxo, images or prices compared with the DP. I've searched google but no results for nortech inlet manifolds for saxo. For DP the best price I've found was 1.015 GBP. :y:

Cheers!

You'll have to enquire with them,
I'm not sure if they have done one,
But they will make anything.

The inlet? yes - was a big improvement - I was using the standard plastic inlet previously, but after titch split one at about 26 psi, I changed immediately to the DP one. The inlet welds are a bit cold on mine and it doesn't have perfect penetration throughout, but it's still fine - but lets remember you're talking about a £1k manifold so I'd expect it to be good! :p

The DP exhaust manifold was warped. I told DP. they knew about it, and said there was nothing they can do as it's part of how it's made. Mine was warped bad enough to pull a manifold stud out of the head and blow the manifold gasket. Titch's was warped, but not as bad. Brents (now ollies) was the same. And the three I've seen since. They really should get that fixed...

BUT - all the negatives aside, it does the job I want, and is an "off the shelf" item. Danny made his own, as have others, and have done what looks to be a job just as well. It's doable. :)

you'd think they'd put it through a mill or surface grinder once its all welded up to make the surface flat, that's what Colin Satchell does.

actually, that'd be awesome, Short satchell inlet with sealed airbox and 8 injectors, as long as Bike bodies will take boost.

I had a machine shop mill mine to flatten it out. the bottom bar in this photo is flat. The manifold as you can see is warped in the middle:



A friend has a boosted gsxr1000 - they take boost. I like where you're going with this :p

that is shocking mate.

Was talking to mark1311 on here about these in the summer and the quality of them and the warp factor. IIRC he was making a jig to start making his own version out of better materials and better welds (some we have seen were literally surface welds) not sure if he actually made any but the bloke has the skills and equipment to make them.

£1000 for a decent inlet is alot of money
Rover inlets can be had for £50 ish on ebay and just mod it

Tubo?

SUBO!

I had a 20v turbo one for my car but sold it might get another one

Aye I watched Titch make a rover inlet fit. It's a good solution (although id personally probably go the c2 vts route if staying with a standard inlet as its a direct bolt on, albeit much more expensive lol).

Yes but im a tight bastard ross and didnt pay for this inlet :y:

Martin the work you do on the budget you spend staggers me. I wish I had the know how :oops:

I had a machine shop mill mine to flatten it out. the bottom bar in this photo is flat. The manifold as you can see is warped in the middle

to be fair to DP or anyone making such a weird shaped +compact ex manifold ,they are always going to have issues with distortion
all those pipes of different lengths ,cold drawn bends +then welded --and not left in a jig and heated up to red heat to stress relieve them --its going to bend and nothing will stop it except for a much thicker flange on the head and then it will just move the bottom flange instead
I have to hand it them though they have managed to convince everyone that they need such a complicated manifold in the first place.
Its nonsense and just bling anyway .
same goes for the inlet manifold right over the top
a bmw 740 --4.5litre v8 runs a 60mm t/body up to 7000rpm and makes near 400 n/a ,runs like a sweety at all times --so why when you are cramming in twice the volume of air would you need a 70mm t/body on a 1587cc engine --you don,t
same goes for the primary pipe sizes on the ex manifold ,and to make it worse they all come together and the crossectional area at that point is very restricted
this cuases lots of heat to back up ,add to that the poor airflow around the manifold and you are going to get uneven expansion .

for those of you who want to prove /disprove what I am saying
take tapping from the ex manofld just before turbo --a bit of brake pipe extended out then rubber to a gauge --measure the back pressure required to get your boost required ,then watch it climbs as you go further up the rpm range -- all that wasted power and extra heat you don,t want to make .
I did this years ago with a saab 900 and by bleeding off the extra pressure I increased engine output with std turbo to get a 25% increase on what the turbo was rated at --
the turbo stopped glowing as did the ex manifold ,
this is why the VNT turbo came into being
which brings us nicely on to the choices of turbo,s --DP specifyied the gt28 ,as it was something old fashioned they could get cheaply and its why the lag is so bad and won,t spool up till more than half way up your rpm range
its really is not matched to the engine at all ,just happens to fit same flange as the r5/nissan silva turbo they started the project with .
its big its crude
yes it can make enough power --but its not a good choice due to its physical size .
a smaller turbo with a simpler more compact manifold will do all it needs to do and keep the heat problems to a minimum .
I am suprised some of the turboguru,s have not realised these simple things

If you must have a manifold of that shape then there should be slip joint on all the primaries to allow for this so it can expand and contract without moving everything about .
that will give leaks when its cold ,but on a race car of ultimate spec thats not a problem .
look at your favorite std turbo cars ,which with chipping etc can make more bhp than your saxo , + alot easier and you will find very simple cast manifolds and even some of those have a slip joint to stop cracking of manifold .
the bolt holes will be at least 2-3 mm larger than stud size for same reason to allow for expansion
the large primary sizes on the tubular manifolds will make more lag as the gas speed will be lower ,untill it hits the restrictive turbo flange,which will cause turbulance and not do what a std cast manifold does
most are split into 1+4 and 2+3 to give nice puses to the turbine
best example I can think of at present is the toyota mr2 turbo --which uses the twin entry ct28--boosts from 1500rpm --strongly and can give 2.0 bar below 3k--you can,t use that much boost anyway --,its just to show what a well matched manifold+turbo can achieve
If you study the manifolds of the cars your turbo came from you will probably find they are larger where they join your welded up flange but are much smaller in primary size--to keep gas speed up.
now common sense says if the turbo maker decided on that flange size ,then you do not need any larger sizes in your manifold ,anywhere
and if there were any great performance gains to be had with a fabricated manifold they would have used one --costs would be minimal for them when they are making thousands of them
If there are any small power losses due to the manifold --they just up the boost a bit .

now it is said that turbo,s sap less power than super chargers and I would agree to an extent --
with s/c we make the power then use some to drive the s/c unit ,but if the turbo installation is correct there should be less power loss than the s/c
studying lots of graphs and print outs for years from both s/c and turbo installs ,at boost levels the s/c can attain ,as its limted to around 1.2 bar for most installs ,
then the results do not back it up
the conclusion is simple
the expected gains from using a turbo do not manifest themselves because there are other losses --
the turbo has the advantage of being able to run higher boosts,so can hide the power losses very easily ,which show up by excess heat and fuel consumption .

It is well known I do not like turbo,s in small front wheel drive cars ,due to the non civilised way the power is deleivered with all that means to drivability and damage to transmission etc.
It is also why the std modern 200bhp+ turbo cars need all the tricky gadgets ,motorised throttle electronic boost ,ESP ,traction control etc to be acceptable
I am not against turbo,s at all and I am writing this ,as much to help with any new proects .not to slag off turbo power in general

Thanks for taking the time to write that John - appreciated :)

I don't argue with any of what you've written - the 70mm tb is something I would change if starting again for sure (back to 60 or 65mm max). On a small displacement engine with a large tb, making part throttle behave nicely is a real pain (by part throttle I mean the first 1-2% opening). Crawling along in traffic on/off throttle territory.

You've hit the nail on the hear re the warped manifolds - they do use a jig but I think what they should do (IMO of course, I'm not a metal worker) is use a much thicker flange (half as thick again perhaps) and mill it down once finished. So factor in the (less) warping due to the thicker flange, then mill it snooker table smooth. But of course, that costs money and a little extra time.

Wow, probably the first time in a while I agree with most of what you say there John :D

I'll have driven every form of aspiration/boost in my car soon so I'll give a small write up to how I have personally found each option to be.

[B][You've hit the nail on the hear re the warped manifolds - they do use a jig /B]

Yes for sure they use a jig to make it ,but ,they do not then stress relieve it AFTER welding by heating ,still in a jig ,all up evenly in a big oven +then cool it slowly