Race Engine Forum UK

I thought I would show some of my current work- S1600 type Peugeot/Citroen head so you can point me in a better direction if you see a better way.

You may already know that these little engines produce in excess of 200bhp from 1600cc, so RPM and cylinder filling at high RPM are the key areas.

Some history-
My previous head was based on a std valve due to time restraints and we were seeing 198bhp with piper cams on a standard bottom end (just machined for valve clearance). The torque below 6000rpm was poor and starting was also poor regardless of mapping. This was mainly due to the low dynamic compression of the bottom end (std with pockets making it lower than std) and the addition of the cams with 120thou of overlap at TDC. An identical head prepped by myself for myself made 174bhp on a Cup engine (std engine with group A cams) and addition of Throttle bodies and ECU. It however had a good torque curve.

This season things are being done right- both engines have Steel cranks/steel rods/Slipper S1600 style pistons.

The standard head has 28.8mm inlet valves and has a bare port flow of 93cfm.

The Citroen C2 engine has a similiar design but uses 31mm inlet valves.

I have inserted the 106 head for 31.7mm inlet valves (21%more valve area than std). Unfortunately I have to cut the seat on the insert first rather than later, so I have used my previous seat combo- 70/45/30.

Here is a picture of the head on the flowbench with the large seat inserts. The bare port flow was much the same even with the bigger valve- 96cfm. As w would have expected as the rest of the port/throat is standard diameter.



I then added the Kitcar style throttle bodies I use (these go straight onto the head and have the same downdraught angle as the head) Bareport flow dropped slightly pointing to a need to look at the exit section. BPF is now 95.3cfm



From previous velocity probing tests - I found that a lot of the flow is high in the port and near the bifurication (port divider) so these sections will be worked on today.

here is a picture of the bottom end.



More to come soon- comments welcomed.

Steven

hi Steve,

did you actually mean to post this in GC Q&A? Looks like you know what you're doing already!

GC

Yea of course, Id welcome any input.

all engine work is experimental to some extent, if others have better ideas then I'll try them by all means.

If you want to move it , if you feel it is more appropriate elsewhere then please do so.

Id welcome your comments anyhow.

Steven

Steve, hi

No worries, it's very welcome here, just checking!

My first remark would be that on a head that is already 'optimised' - no, you won't get more bpf from a bigger valve unless you bore out the throat by a proportionate amount. I imagine you know this. So if bpf is not higher, you won't get the full benefit of the bigger valves at higher lifts. Judging by the throttle-body shot I figure it's got quite a good downdraft angle and in that case you might well be better off with 75 deg throat. Whether it works better with radiused seat angles or not I don't know in this case.

I don't think I have worked on one of these so I'd be interested to see your flow graphs, some closeups of port showing what type it is, the SSR region b4/afta, the valve head shape.

Hope that is a good start,

GC

Pics removed to be replaced by better ones on request of GC.

Thanks for the tips, I'll try and provide some of the details you want later including graphs . The head design is very similiar to the 206 16v head except it doesnt have the valves pushed into the corner as much and there is no bump in the inlet throat and less port bias to outside of cylinders.

Here is summary of yesterdays work.

I wanted to test the std head with the big inserts in it for completeness. I was more interested to see what difference the throttle bodies had on the flow as I had not tested this previously as they only became available mid way thru the season.

Here is the chamber with the inserts fitted, notice the step in the throat due to machining.



Here is the inserts being blended into the throat with a carbide and the throat being opened by hand close to size.



The SSR is fairly typical of a downdraught head- having not muc of it at all, so it was just radiused as before in the std valve head i developed.

The std peugeot guide is a nice bronze type material so I didnt want to "shave" it so I pressed it back and worked the port with the carbide in the areas where port velocity was highest.-The bifurication and the roof of the port.

I then downdraughted the port slightly as it did not have a perfect line of sight from the manifold to the port divider. Here is a pic of my rough template so I can scribe a line.



The head was then finished with 80 grit and then 120 grit to give the picture below.



I pressed the guide back in so it didnt affect the flow readings and we were back on the flowbench by 10pm for the final test.

Result is now BPF up from 96cfm with the big valve to 123cfm. I have one last thing to try before I move on to the valve in flow tests and then produce some graphs for yous.

Steven

I have added the throttle bodies again to the head as it is in near final form but this time the flow went up (not down as previous.

before as std with big valves 96cfm bpf
with throttle bodies 95cfm

modified form 123cfm
with throttle bodies 126cfm

I can only equate this to the fact i did a proper line of sight from the bodies into the port wherea in std form there was a slip dip.

I have only ever seen one other head give an increase with a manifold added and that was a peugeot 306 gti-6,

I have measured it 10 times.. and im sure im right.. any thoughts Guy? or others?

Hi Steve

It's as real as it looks I'd say! It's is not a common occurence, but can happen - depending on the orientation of the port that adding intake components outboard of the head can improve flow; I saw an improvement with fitting inlet manifold on a Peugeot S16 306 2 liter head a while back, see graph and photo.

As you indicate, if it happens for real and isn't just a measurement error (I double-checked mine too!) it's because, on your modified port - the extra outboard section probably biases the flow in an 'advantageous' direction, ie: gives better flow distribution thru the valve throat. Doesn't necessarily work, as you saw, on the port in standard trim.

You get the reverse too, where a manifold disrupts the preferred airstream direction and robs flow, I wrote about this in another thread here, downdraft vs sidedraft.


GC

Well the preliminary dyno results are in-

After 2 hours running in and mapping on our rolling road- it made 207bhp / 140lb/ft. Peak power is 8200rpm with useable rev range of 5-9000rpm. I was a little disappointed initially but the engine is still a little tight and I have not spent any time playing with ram lengths/ cam timing/ 8 injectors. All that will come when we install the latest TAT data aquisition gear for the dyno next month.

However on its first event- I broke the class hillclimb record by more than half a second, so i suppose the proof is in that.

Thanks for the replys Guy, and I dynoed a wee 8v Peugeot that I pointed the client in your direction for a better head, did he phone you?

Steven

Hi Steve,

Your S1600 dyno test motor above is 1600cc?

G

yea its 0.25mm overbore- 1596cc .

Steven

Steve, hi

on a 1600 16v unit, I think your 207bhp & 140lbf ft is really an outstanding result! There won't be many around who can (genuinely) better that.

Well done indeed,

G

been away from web for a while so heres an update- thanks again for your valued input,

results for 2008-

NI hillclimb championship winner
NI Sprint championship winner

3 new NI hillclimb class records, one in British championship.

Leaders championship (based on class records) runner up.

The second engine produced 208bhp and 143lbft, and won both championship in class 4, with 1 new record.

Some new development for 2009- ( new data aquisition system on dyno should hopefully help home in on the mapping).

6 speed straight-cut box, and works airbox.

Steven

MODEL POST!

Comprehensive background info on the engine prep, dyno results and OUTSTANDING race results.

Well done indeed Steve and thanks for publishing here.

GC

BTW - if you have any car pictures - esp with engine on view- please post them here.

the first one is a team picture of both cars.



here is an action photo.



and here is our dyno (rolling road ) with a customers car on for mapping.

Hi Steve,

Which engine is this? An s16 engine or what? Cannot quite figure out which engine it is. Would like to stick one of those engines in to my Peugeot 205 which is a project for the Danish Endurance Cup (DEC), and i would like to know which engine it is so that i can find out whether or not it will fit in a 205. And furthermore - how much is one of those heads if i could buy one from you? ;) (or from GC perhaps?)

Stefan