Changing The Mi16 Engine Characterists.

[SweetBadger 91]

Definitely use #4 on the inlet and #2 on the exhaust. I never use a #2 on the inlet. It's too retarded for a performance cam.

 

Ok, I'll probably change them round so that #4 is on the inlet, but I am getting conflicting info after reading this:

 

http://forum.205gtidrivers.com/index.php?s...pic=14992&st=40

 

As I'm using a 1.9 box it'd be advantageous to have the extra low down grunt, but the conclusion from the thread above was that the engine ran significantly better with the #4 pulley on the exhaust cam... Has anyone else actually done a direct comparison between the 2 setups?

 

Would getting hold of a #3 pulley for the inlet be a better compromise for an MI using standard internals and cams, or should I just stop worrying about it and shove the #4 pulley on the inlet?

[petert 550]

Ok, I'll probably change them round so that #4 is on the inlet, but I am getting conflicting info after reading this:

 

http://forum.205gtidrivers.com/index.php?s...pic=14992&st=40

 

As I'm using a 1.9 box it'd be advantageous to have the extra low down grunt, but the conclusion from the thread above was that the engine ran significantly better with the #4 pulley on the exhaust cam... Has anyone else actually done a direct comparison between the 2 setups?

 

Would getting hold of a #3 pulley for the inlet be a better compromise for an MI using standard internals and cams, or should I just stop worrying about it and shove the #4 pulley on the inlet?

 

Have a look through some old threads about the flow of 16V heads. The exhaust ports don't need any help. Think about what happens in the cycle if you open the exhaust valve a bit earlier and close it a bit earlier. If you want the most useable torque, put the #4 on the inlet. Somewhere in the middle is a #3. Swap and see. It's a simple job to swap if you don't like it.

[C_W 3 1 Cars]

Whats the best for exhaust cam then? Mine runs a #4 exhaust and #2 inlet I think, originally out of a BX 16v.

[fiji bob 0]

my engine came from a 1991 3 row 405 and had a 4 pulley.

[petert 550]

Whats the best for exhaust cam then? Mine runs a #4 exhaust and #2 inlet I think, originally out of a BX 16v.

 

Swap them around if you want more torque. As I said earlier, I always use a #2 on the exhaust, the same as that Peugeot spec. sheet I attached earlier.

[SweetBadger 91]

I tried swapping them around last night, but when pulleys were locked with the timing pins there was no way I could set the tensioners up so that they would remain spot on with the timing pins removed.

 

With the right hand tensioner set to max tension the belt was still too loose, meaning that the only way to get the belt to the correct tension was to use the left hand tensioner which in turn pulled the pulleys out of line with the timing holes... I'm sure they weren't too far out, but with both pulleys rotated slightly anticlockwise to get the right tension, doesn't this mean that they are both slightly retarded?

Edited April 4, 2006 by SweetBadger

[petert 550]

You should still be able to lock everything up with the pins and adjust it correctly. Remember, it's the cams that are moving, not the pulleys.

[SweetBadger 91]

You should still be able to lock everything up with the pins and adjust it correctly. Remember, it's the cams that are moving, not the pulleys.

 

Yep, just retentioned the belt and it all lines up fine, dunno why I couldn't get it right yesterday .

 

Thanks for the info, just gotta get it in the car and try it now...

[d-9 0]

Petert, could you post up a pic of one of your offset keys? Intersted to see what they look like, do you ship to the uk?

 

Are the numbers stamped on the outside of the cam pulleys so you can see them if you remove the cambelt cover?

Edited April 6, 2006 by d-9

[Paintguy 0]

Are the numbers stamped on the outside of the cam pulleys so you can see them if you remove the cambelt cover?

Yep.

 

Had a look at mine out of interest, after seeing this topic. Just pulled off the cambelt cover and there they were - two little number 2's.

Edited April 6, 2006 by Paintguy

[petert 550]

Petert, could you post up a pic of one of your offset keys? Intersted to see what they look like, do you ship to the uk?

 

My macro photography attemps are very poor. This is a 4 degree (crank) key:

 

 

 

 

$35 inc. postage to anywhere.

Edited April 7, 2006 by petert

[KRISKARRERA 2 1 Cars]

I know I've never changed a cambelt before but I can't even begin to imagine how that works.

[Guest Cartooner]

here is two graphs of a mi16 std engine with twin 45 dellorto carbs, you can gain a bit of bhp and a fair amount of torque by swinging the std cams.

 

far better delivery of bhp

 

and a good whack of low end torque

 

let the handbags comence

 

Why am I missing the clue here? What I understand is that the blue lines are for the advanced inlet cam( no.4). I can't see the advantage here. On both graphs bhp and torque figures are higher on the red lines from about 2200 revs. If you launch the car from a stand still with 2200 revs, You'd allways be better of with the red lines. Whilst cruising I am almost allways above 2000 revs even with the 8V engine. ???????? Do I misread the graphs or are the red lines for no.2 exhaust and no.4 inlet.?????????????

[SweetBadger 91]

Why am I missing the clue here? What I understand is that the blue lines are for the advanced inlet cam( no.4). I can't see the advantage here. On both graphs bhp and torque figures are higher on the red lines from about 2200 revs. If you launch the car from a stand still with 2200 revs, You'd allways be better of with the red lines. Whilst cruising I am almost allways above 2000 revs even with the 8V engine. ???????? Do I misread the graphs or are the red lines for no.2 exhaust and no.4 inlet.?????????????

 

I think the two lines are for power and torque, you compare the 2 graphs - 1st for #2 inlet and 2nd for #4.

 

I've now tried it with #4 on the inlet cam (before having to strip the sodding thing down again) and compared with my old MI it definetly had more low end grunt and was more tractable (still nothing like a 1.9 8v though) in my opinion however it took a big chunk out of the fun factor. It just didn't feel happy revving over about 5800 rpm so I'll be swapping it back to standard - the top end reminded me of how the 8v used to drive, too much of a sacrafice to make for a bit of extra power down the rev range in my opinion. I think maybe a #3 pulley would be a better all round compromise.

[Guest Cartooner]

Still the first one says bhp with a blue and red line. The second one says torque with a blue and a red line. the way I read it the blue line is only better on both bhp and torque below 2200 revs. That's not what I call usable gains, and that all with major losses above 2200 upto the red line. Hmm, better stick with no.2 inlet pulley, I guess. Can anybody convince me to chose no.4.

 

The theory I heard about the campulley's is the following: No2 inlet was chosen mainly for engines that use many aux. pumps ( airco/ hydr.pump on citr./ power steering) to maintain idle quality with these powerrobbing features. ( mark the words theory and heard though).

[petert 550]

Can anybody convince me to chose no.4.

 

Only if you've got a bigger cam that needs a smaller angle. #3 or an offset key is a better choice for a std. cam.

[saml666 0]

I'm in danger of everyone telling me "nooooooooo, you'll lose power" or "why not just run an 8v" but hear me out (BTW, my Mi16 internals are 100% standard - if I was on uprated cams / head etc I wouldn't do this)...

 

Deep Breath...

 

...I'm going to try running my Mi16 on twin 40's...

 

...there, I said it!

 

OK, the story is this ... theres a guy on Ebay who does EXTREMELY thorough rebuilds of Dellorto carbs, turns out he's local and several people I know who go rallying etc rate him very highly. I went to him for 45's (as thats what everyone else runs on mi16s right?) and he said if I'm keeping it std try 40s on 35mm chokes...

 

...his reasoning was that I would get a really tractable more torquey drive, something much more suited to fast road use with power where it would really get used without bouncing off the rev limiter all day.

 

He also said if it also goes "Pete Tong" I can chop them in for 45s!!!

 

So I've nothing to lose apart from time, and I'm willing to give it a shot.

 

It seems a huge amount of this is down to personal preference / driving style and simply "what people want" - these are my choices / reasons:

 

I like doing engine conversions and I like the idea of running a 16v engine in a normally 8v car, so I guess thats why I don't just stick to an 8v.

 

I agree that some people will think the engine is flat as the difference between 3k and 4k revs is so great on an Mi - its subjective. I drive all sorts of cars and some feel fast when other don't due to delivery, soundproofing etc. Personally I always think luxury cars "feel" fast as they're so effortless, my 4.6 V8 scimitar feels slower as its so bloody rattly and boat-like but its straight line performance against Porsche 911s, Chimaeras, Scoobys etc speaks volumes - but thats enough willy-waving for now...

 

...one things for sure, the guy that went for a ride in the mi expected a bigger shove... but don't we all... When I got the V8 back from its rolling road session I have to say I was disappointed that it didn't snap my spine and cause me to black-out, but you need to drive for quite a while in a new car before you really get the most from it... then you realise how damn well it goes.

 

Anyway, going back to topic

 

The theory is that I may not have the highest BHP Mi on the road but it will feel GREAT and shove you where you want it to. BTW, am using carbs, again, 'cos I just like 'em They're cool

 

The Scim often out-performs higher BHP cars of similar weight (like turbo Subaru's etc) because of its torque. You sacrifice some BHP up top and gain mountains down low and average out with a car that makes more power for longer.

 

Horses for courses

 

I have to admit though, I can quite see myself going to a decent big valve head, 45s etc next year as contrary to one of the earlier posts, surely its the small cars that like the high revs? Its big fat motors that need torque to get their heavy arses off the line - like my scim (it might be fibreglass but its effing thick in places, a lotus elise it is not!)

 

Well, thats more than enough for one day - I don't usually type so much but its just my experience of big and small engines, heavy and light cars and what I like.

 

The next guy might like something else completely, and thats why we're all different. Messing around with cars is great, the best reason in my opinion for doing something is when someone else says it won't work*

 

Cheers, Sam

 

*except welding an old fuel tank, that'll make your eyes water...

[Ahl 4]

I don't know where the hell you freaks have got the #2 and #4 cam nonsense from. Your trying to simplify or complicate things too much.

 

Those graphs simply show the same cams, but the red line shows the cam(s) advanced quite a lot, though it isn't specified.

 

As you can see, it makes better power and especially a s*it load of torque which is what actually makes the car fast.

 

[edit] good post above btw, spot on.

Edited May 1, 2006 by Ahl

[petert 550]

I don't know where the hell you freaks have got the #2 and #4 cam nonsense from.

 

What's nonense about it? Either you understand the effects of advancing/retarding cam timing or you don't.

 

Some people spend serious amounts of money on vernier pulleys, others do it with factory parts or offset keys.

 

As for the graphs, Jeram didn't say how much he "swung" the cams, or what the original timing figures were, so they're basically useless anyway.

Edited May 1, 2006 by petert

[huxley309 0]

Sam i know one or two who run 40's on the 8v to gain in the low/mid end and it works well so should make your mi more torquey but tbh after i had the bodies fitted that improved the mi in this area anyway

 

It's this reason why i chose a larger bore and std valves as i wanted to maintain tractability whilst keeping the screaming nature that is the mi, and after driving her i feel i pretty much got the balance right

[saml666 0]

Sam i know one or two who run 40's on the 8v to gain in the low/mid end and it works well so should make your mi more torquey but tbh after i had the bodies fitted that improved the mi in this area anyway

 

TB's... mmmmmmmmmmmmm... Maybe next year... (Sighs longingly)

 

Actually, TBs would be a more worthwhile upgrade than just moving to 45 Dellortos but for now am running cheap'n'cheerful - just gotta get on the road, I only got about 100 miles in and 20 minutes of tarmac autotest before the 8v died

[Ahl 4]

As for the graphs, Jeram didn't say how much he "swung" the cams, or what the original timing figures were, so they're basically useless anyway.

Excuse me for being slightly drunk , as said, what I meant is that those graphs are not specific to the #2 or #4 pulleys.

[KRISKARRERA 2 1 Cars]

Exactly Ahl.

I'd like to see a before and after graph for Peter's offset key thingy.

[Guest Cartooner]

Excuse me for being slightly drunk , as said, what I meant is that those graphs are not specific to the #2 or #4 pulleys.

 

You're absolutely right and like Peter allready said Jeram's graphs are useless here. But the topic subtitle is 'how to get a flatter powercurve'. My question is: Can this be achieved by only advancing the inlet cam a few degrees.( by means of changing pulleys, offset key or verniers) Would this work on a otherwise standard engine. My engine (D6C /BX) came with 2/2. Why did people at PSA use different pulley's?. Is it the application( 4x4 ) or Emission controls or aux pumps on the engine.

 

Isn't there a relation between ECU nr.s and pulleys used.( I have ECU 119 with pulleys 2/2) Surely a different cam timing might need a differently mapped ignition?.

 

Is it safe to say, that the use of different cam timings has something to do with the younger engines using more ignition advance made possible by the slightly lower compression and the use of a knock sensor?

Isn't inlet cam advance limited by the absence of detonation control on the older engines(thus 108 degrees).

 

Oh my God why didn't I finish my school. My head should b e filled with more facts and less questions.