Intake Manifold On 205 Gti

[Henrik P 0]

Hello.

at the moment i am working on my head to my 205 GTI. But on one point it's hard to improwe the flow. And thats the intake manifold wich i think has a bad design when it comes to flow. So i was thinking about making my own manifold and stil keep the std throttle and afm. My plan was to use the old mounting plate on the std manifold where the nozzles are fittet and then weld some runners ond the mounting plate, at the end of the runners i will weld a plenum champer around them an on the end of the champer i will weld the throttle on so i still can use the std afm.

 

What does people say to my idea? Is it a waste of time ore has it been done before with a god result?

 

Henrik

[Batfink 201]

Hello.

at the moment i am working on my head to my 205 GTI. But on one point it's hard to improwe the flow. And thats the intake manifold wich i think has a bad design when it comes to flow. So i was thinking about making my own manifold and stil keep the std throttle and afm. My plan was to use the old mounting plate on the std manifold where the nozzles are fittet and then weld some runners ond the mounting plate, at the end of the runners i will weld a plenum champer around them an on the end of the champer i will weld the throttle on so i still can use the std afm.

 

What does people say to my idea? Is it a waste of time ore has it been done before with a god result?

 

Henrik

 

something more like the gti-6 manifold would work. If I was doing it I would look to keep similar intake lengths but look at using the plenum to match the airflow to each cylinder.

[Henrik P 0]

something more like the gti-6 manifold would work. If I was doing it I would look to keep similar intake lengths but look at using the plenum to match the airflow to each cylinder.

 

But the GTI-6 manifold dos'nt fit do it? I have drawen a little drawning of what i had i mind

manifold.bmp

[jengis 0]

Just out of interest, what is the reason for saying the standard inlet manifold has poor flow? Any particular area that is restrictive? I would like to know what could be improved also if anyone has proven mods.

 

A larger plenum seems a good idea in theory but with that amount of custom work surely individual 'bodies or carbs would be more cost effective.

[Saveit 0]

I have attached a picture (made by Guy Croft) showing where and why the 205 gti doesnt flow that well.

Edited February 8, 2009 by Saveit

[pug_ham 244 3 Cars]

Maybe that picture explains why the plastic inlet from the later M1.3 cat equipped cars & the ZX Volcane with MP3.1 ecu is claimed to flow slightly better.

 

The high viscous (drag) loss due to cast roughness on manifold interior won't be as severe.

 

Graham.

[Henrik P 0]

Just out of interest, what is the reason for saying the standard inlet manifold has poor flow? Any particular area that is restrictive? I would like to know what could be improved also if anyone has proven mods.

 

A larger plenum seems a good idea in theory but with that amount of custom work surely individual 'bodies or carbs would be more cost effective.

 

Year carbs ore bodies will be more effectivce. But it's expensive and illegal in Denmark. And a manifold is not that expensive if you make it your own

[Henrik P 0]

I have attached a picture (made by Guy Croft) showing where and why the 205 gti doesnt flow that well.

 

Thats right. That is one of the places i have heard that it dosn't flow well.

 

But has anyone tryed making there own manfold with the std AFM?

[Saveit 0]

I wouldnt bother Henrik. I dont think you will end up with any significant gains over the 205 gti inlet manifold although there is room for improvement on this one. But give it a go if you like and open a thread in the Car Works section, and let us know your results. Could be interesting.

[Henrik P 0]

I wouldnt bother Henrik. I dont think you will end up with any significant gains over the 205 gti inlet manifold although there is room for improvement on this one. But give it a go if you like and open a thread in the Car Works section, and let us know your results. Could be interesting.

 

Maybe it will be the next winther projekt then

[benlilly 0]

Here are some flowbench results showing the OE manifold losses, made by Guy Croft. Def. room for improvement but making a better manifold isn't an easy task and the OE injection isn't well suited to dealing with the increased flow.

 

205_GTi_Flowbench_Results.pdf

Edited February 9, 2009 by benlilly

[Baz 421]

What about using the Xu10 inlet manifold that uses a similar TB to the Mi16, this looks to have at least better curvature than the std Gti inlet for the air to follow. A search may uncover somwthing as i'm pretty sure it's been talked about before, certainly about using with an Xu10t anyway.

[Jakob 1]

Here are some flowbench results showing the OE manifold losses, made by Guy Croft. Def. room for improvement but making a better manifold isn't an easy task and the OE injection isn't well suited to dealing with the increased flow.

 

205_GTi_Flowbench_Results.pdf

 

 

It dosent tell much about the manifold. Actually it flows better with the manifold than none.

Most interesting is however that he among others (hi lift cam) went down from 42,6mm to 42 inlet valves !!!! and got the 174hp on the 1.6 engine, (reducing valve shrouding)...!!

For those who use 43mm XU10 heads on 83mm XU9 bore should pay attention to this one...

[Saveit 0]

Jakob i will be doing the XU10 conversion soon, and i will post my results in here. Then i believe we will have a final result that will tell us whether this XU10 conversion is worth it or not.

[bensonmi 4 2 Cars]

how about a inlet of a bx gti? as they are tubular or are these the xu10 ones that baz is on about?

when i fitted a bx gti engine in my 205 before the inlet noise was a lot better and it went better than my old 205 gti engine that was fitted previously.

but i think the inlet ports were a different shape so you might have to use the whole bx head,but then you might as well use the whole engine if you can get one.

and if you do that you might as well use the management for smoother running.

[James_R 3]

The 405SRi and BX Gti engine's use a different head with downdraft ports which are meant to have better flow over the std GTi ports, and the engine have flat top pistons for a better chamber shape, although compression needs sorting.

[benlilly 0]

It dosent tell much about the manifold. Actually it flows better with the manifold than none.

 

Think you have miss-read the graph. The two to compare are the top two from the legend on the right. Flow is lost at higher lifts with the OE manifold.

[Kobayashi 35 2 Cars]

Maybe that picture explains why the plastic inlet from the later M1.3 cat equipped cars & the ZX Volcane with MP3.1 ecu is claimed to flow slightly better.

 

The high viscous (drag) loss due to cast roughness on manifold interior won't be as severe.

 

Graham.

 

would this be a direct swap matching any XU9 Head? or does it need any mods?

 

thanks!

[RossD 44]

Maybe that picture explains why the plastic inlet from the later M1.3 cat equipped cars & the ZX Volcane with MP3.1 ecu is claimed to flow slightly better.

 

The high viscous (drag) loss due to cast roughness on manifold interior won't be as severe.

 

Graham.

 

GC talks about manifolds on XU heads

See this topic here, GC actually reckons the plastic manifold is worse than the original Aluminium one :s

[DamirGTI 342]

Graham was referring to an OE 205 GTI plastic manifold , not this 306 one in the thread late 205 GTI-s , and as said Citroen ZX 1.9 8v cars , had the same type/design of the inlet manifold but not made out of aluminium , they where made out of plastic ! .. i'll try to dig a picture , i did have one somewhere ..

 

Damir

[DamirGTI 342]

...i can't find picture of 205 with such manifold , but here's one on Citroen ZX 1.9 (same thing anyway) :

 

 

Damir

[Anthony 1,003]

the OE injection isn't well suited to dealing with the increased flow.

I disagree. Being AFM based, the standard management is actually very good with dealling with extra flow for the most part, unlike for example systems that use MAP sensors for load (S16, GTi-6 for example). The reason being that AFM's measure airflow directly, and hence extra flow means extra fuel (to a point, obviously)

 

A good example of compensating for increased flow is that you can use 1.9 Jetronic management on an Mi16 and it'll still fuel pretty well (the ignition curve is ill-suited though), or run 1.9 engines on 1.6 management with no ill effects.

[benlilly 0]

I disagree. Being AFM based, the standard management is actually very good with dealling with extra flow for the most part, unlike for example systems that use MAP sensors for load (S16, GTi-6 for example). The reason being that AFM's measure airflow directly, and hence extra flow means extra fuel (to a point, obviously)

 

A good example of compensating for increased flow is that you can use 1.9 Jetronic management on an Mi16 and it'll still fuel pretty well (the ignition curve is ill-suited though), or run 1.9 engines on 1.6 management with no ill effects.

 

Hi Anthony,

 

I thought that the flap was wide open from peak torque and then fuelling above this rpm point was governed purely by the resistor values in the ecu. If flow is increased then the flap is going to be wide open earlier and at higher rpm the fuelling will go lean.

 

What do you think.....perhaps my reply should have been 'the OE injection isn't well suited to dealing with the increased flow at higher rpm'

[Saveit 0]

Hi Anthony,

 

I thought that the flap was wide open from peak torque and then fuelling above this rpm point was governed purely by the resistor values in the ecu. If flow is increased then the flap is going to be wide open earlier and at higher rpm the fuelling will go lean.

 

What do you think.....perhaps my reply should have been 'the OE injection isn't well suited to dealing with the increased flow at higher rpm'

 

Exactly my thought!

[pug_ham 244 3 Cars]

would this be a direct swap matching any XU9 Head? or does it need any mods?

Direct fit onto any XU5/9 GTi head.

 

Throttle body would need to be swapped to suit the different type of TPS as teh vbolt spacing is very slightly different iirc.

 

 

GC talks about manifolds on XU heads

See this topic here, GC actually reckons the plastic manifold is worse than the original Aluminium one :s

Thats on the XU10 engines like Damir said & not the ones from the XU9 engiens I mean.

 

Graham.