Mi16, Which Cams?

[IanH 1 1 Cars]

Hi, I would like some opinions please if you have the time / inclination.

 

I own a '93 205 with a 1988 Citroen D6C 1905 aluminium block engine, 160bhp standard

The car is running Jenvey throttle bodies, omex 600 management, bosch 803 injectors, longman manifold going to magnex system. The engine was totally rebuilt by myself and the internals are fairly standard except for 11:1 CR, ARP con rod bolts, baffled sump, slightly flowed head, PT1604 kent cams on vernier pulleys and a rev limit of 7.5k.

 

The car used to run Kent PT1602 cams which are fairly mild, and was mapped with these by Northampton Motorsport a few years back, making 190bhp at the crank. I upgraded to Kent PT1604 cams a while ago and didn't get it remapped. The car runs OK and as you would expect, goes wild at the upper end of the rev range, but doesn't have much guts at the lower end which make road usage a tad disappointing unless you are being an complete and utter hooligan. All as you would expect from a 'cammy' engine.

 

My initial aim for this car was to build a track day toy with occasional use on the road. In reality I use it 99% on the road and it hardly sees a track so I'm thinking that I need some cams that are slightly less duration in order to regain some low end again. If these 1604's are able to make power way over 7.5k then they are not what I need I guess. Or maybe they just need mapping, I don't know. Ive even considered putting standard cams in again, but that would probably be a waste of all the other mods?

 

I would like to know whether these cams are too wild for this engine spec considering the rev limit and my intended usage which seems to be more road based than track, and whether I need to go and get a remap in order to get the most out of these cams, or indeed if anyone has some recommendations about which cams to use for what I intend for this car. I have no problem using other manufacturers, and PeterT's have caught my eye a few times

 

Cheers for any help.

 

PT1602:

Application Sports ' R '
Power Band 2000-6500
Cam Lift(mm) 10.94
Valve Lift(mm )10.94
Duration 264 Deg
Timing 22/62 62/22
Full Lift I 110 Deg E 110 Deg
VC (mm) 0.00
LTDC I 1.65mm E1.40mm

 

PT1604:

Applications Competition

Power Band 3500-7500

Cam Lift(mm) 10.84mm Inlet/Exhaust

Valve Lift(mm) 10.84mm Inlet/Exhaust

Duration 316 Deg Inlet/Exhaust

Timing 52/84 84/52

Full Lift Inlet 106 Deg ATDC/Exh 106 Deg BTDC

VC (mm) 0.00mm Inlet/Exhaust

LTDC 2.56mm Inlet/Exhaust

Edited April 19, 2017 by IanH

[welshpug 1,657]

that looks a bit of a monster of a cam! not enough compression I would imagine to make the most of it.

 

there's going to be massive holes in the map given the difference between the two camshaft profiles, a map goes without saying would make quite a difference.

[TAG 25 1 Cars]

How have you obtained 11:1 CR?

PeterT stage 2 cam would perhaps be a good choice for you.certainly nowhere near the duration you say your current cams have.

[IanH 1 1 Cars]

Yep, that stage 2 grind is definitely on my short list.

 

I got 11:1 by sending the bare block and liners off to MASS Racing and asking them to deck it properly and sort the wet liner protrusion out so that it gives me at least 11:1. They did they work and confirmed the CR so I know its good. I knew at the time I wanted a bit of a monster cam in there and having read around the subject a bit, realized I needed this CR or better to make it worth while. I also asked them to check the valve spring rates which all check out at 75-80 lbs, and do the maths for the piston to valve clearance which was all good. The trouble is, I don't think I want to rev the thing close to where it will realise its potential, and the usage I want to get out of the car has also now changed.

[TAG 25 1 Cars]

Decking the block so that the pistons are flush will give 10.8:1, and when I did some quick calcs of the combustion chamber, 8 thou skimmed from the head should net another .2 of a compression ratio (and bring chamber cc from 39 to 38cc), perhaps this is what Mass did for you (or perhaps the pistons sit proud of the block at tdc)

 

Have you seen Peter's website? (taylor-eng) He has a lot of info on his cams there, perhaps its worth dropping him a line as well.

[petert 586]

Unfortunately Kent never publish the duration @ 1mm which gives a much better representation of the cam size. For the PT1604 it's 244 deg. In comparison, my 16H426A grind is 236 deg @ 0.050", which would equate to approx 241-242 @ 1mm. Thus very similar in that respect. Additionally, if you compare lift @ TDC figures on a 106 deg centreline, very similar.

 

PT1604 - 2.54mm (0.100")

16H426A - 0.106"

 

So again, you can see once the valve is well off its seat the duration is near identical. It's what's happening before that however, that changes the build requirements of the engine. The PT1604 has very long opening and closing ramps, which you can see in the advertised duration figure of 316 deg. In comparison, the 426A is only 271 deg. Always remember that the compression stroke doesn't start until the inlet valve is closed. Thus the PT1604 needs a lot more static compression. With 11:1 the 426A will have more dynamic compression and thus a wider power range compared to PT1604. Both cams are going to make power to 7500.

 

The PT1604 does have more total lift, which is of course free hp. So theoretically it should make more total power. It will have a narrower power range however. You pay for that lift in dollars however, as that profile has to be ground on a new billet. In comparison, the 426A can be ground on a standard cam. Thus far cheaper.

 

The limit of the hydraulic lifters is approx 7500 anyway, thus it's pointless making power past that. So in my mind a fast opening & closing cam is always going to be better overall.

 

Like all cam grinders, the PT1604 master would be used in other overhead hydraulic bucket engines. They would never have designed it specifically for the XU9J4. The PT1603 is 241 deg @ 1mm, thus very similar and with less total duration, a far better hydraulic grind for the XU9J4.

 

To further illustrate this, a client in NZ changed from 1604's to my solid 400A/402A combination and picked up 20hp with more torque everywhere.

Edited April 20, 2017 by petert

[Type-R 3]

Peter do you do a grind for a mostly stock Mi16 to work with solid lifters and keep the bottom end torque?

[petert 586]

The Stage I or 16H426B is best. No point in changing to solid unless you want sustained 7500 and beyond. It's also a fast opening grind.

[IanH 1 1 Cars]

Looks like I'm heading in the direction of a stage 2 hydraulic grind then, direct from Taylor Engineering.

 

After reading on Mr P.Taylor's website, would I be right in thinking it would be best to find a standard mi16 exhaust cam and some standard Mi16 followers, albeit in good serviceable condition? And would I also need to run the exhaust cam on its original pulley or would my existing vernier pulley suffice?

 

Also, when installing the PT1604's, the engine was out and easy to set up on a stand. This time it will be setting up while in the car, so reading of the flywheel for TDC will be harder. I set them up using lift at TDC, and can find the centre of the dwell easy enough, but if I remember I used the flywheel and a fabricated pointer attached to the block to mark the centre correctly. I guess I could remove the crank sensor and mark the flywheel tooth visible down the hole just like timing a bike engine, but anyone got any helpful ideas?

 

After installing them, I guess I will be off to Northhampton Motorsport again for a remap, whereupon I will be fleeced for £160/hr, dear God :S

[welshpug 1,657]

160 an hour?! ffffuuuuuu.

 

A trip to Cornwall if you can get a slot would save you a fair bit then, and get a very good job done.

[welshpug 1,657]

you can make a wheel to fit on the crank pulley easily enough, the timing pin hole is a very reliable place to locate it, plenty of bolts near it to bolt a pointer under.

[welshpug 1,657]

this is on my gti6, so some dimensions would be a bit different but the method is similar enough.

 

 

[IanH 1 1 Cars]

Yeah that looks good Welshpug, I may have to go down that route for timing it all up etc. £160/hr is feckin' horrendous, and Cornwall is always a nice place to visit.

 

I was looking at PeterT's site and also saw the 2L 26 tooth oil pump pulley upgrade which I didn't do when I rebuilt the engine, and probably should have. I did pretty much everything else to stop it from starving of oil as I used to run a plain sump, no windage tray, no 25psi warning light, no chain cover, standard pump spring, no lowered pickup and sandwich plate etc, all stock standard. I very quickly realised its no good for spirited driving after the camshafts started to eat the damn tappets , hence I've rebuilt it more than once.

 

I was wondering whether its possible to swap out that pulley and chain without dropping the engine. Looks like a bugger of a job but if its possible, would be better than prying the engine out again.

[welshpug 1,657]

yes its possible in the car, just need to take your time so you dont get oil dribbling into the sump-block seal when you re-assemble.

 

 

oil starvation doesn't affect the heads on these, its the primary cause!

[IanH 1 1 Cars]

Doing some research into the oil pump sprockets, it looks like its best to get hold of a single piece sprocket/spacer from an XU10J4RS, with 52 link chain and keyway, all still available from Peugeot.

 

The part number for the sprocket/spacer is #151368 and is no longer available as it changed to #151378 and according to service box and my local pug garage, it also now needs a seal #151492. No idea what this seal is, its not the crank seal, and it isn't needed on the 2-piece design from earlier engines. Only available in packs of 10. Any ideas?

 

Part numbers to help others:

52 link chain: 103310

crank key: 697606

crank seal: 032622

[Andy 105 1 Cars]

You might need to proceed with a little caution. I have one of those one piece 52 teeth sprockets and spacer. Slight snag is that the combined length of the o.e sprocket and spacer together is not the same as the single piece item. In the end I used a 52 tooth sprocket from an iron block Mi16 and a spacer. No idea about the extra seal.

[petert 586]

I agree. Don't get hung up over the 26T sprocket. They wear prematurely compared to the XU9J4 sprocket. I'd use everything else XU10J4 however ie pump, chain guard, windage tray, baffled sump etc.

[IanH 1 1 Cars]

Well, call me an idiot if you like, but I went and got the engine mapped with the PT1604 cams in. Didnt cost as much as I thought, and I had to know what the cams would do after being properly mapped before deciding whether to change them out.

 

Anyhow, after a couple of hours on the dyno, upping the fuel pressure to 4.5 bar and dialing in an extra 8 degrees (!) of inlet cam advance and a bit of exhaust cam advance, I got these figures:

The black trace on the last 2 is the result of the 2009 dyno run of the old engine spec, with the PT1602 cams installed.

 

[petert 586]

Well done and worth the effort. FYI, I had a customer in NZ with a pair of PT1603's, which aren't very much different to PT1604, who wanted more. I reground his PT1603's to solid cams 16S400A/16S402A as per my website. He also fitted new bee hive springs at the same time and went from 170hp at the wheels to 190hp at the wheels (say 240hp flywheel?), with more torque everywhere. He was very happy.

[DrSarty 90 1 Cars]

A little birdie told me that Jenveys give a little more mounted 'upside down', i.e. fuel rail underneath.

 

This may be an old wives' tale, but if you feel like going back for another power run to try this I'd be very interested.

 

I'd meet you there too in mine, which has similar top-end (203), but quite a bit more torque (165). Your torque does seem a little low, which is perhaps why you started this topic. However you have gained more torque across most of the range which probably makes it feel punchier.

 

Mine is a 2.0L with 11:1 and a Catcam inlet.

 

Apart from the torque, I'm surprised you needed 4.5bar fuel pressure. Do you have a fixed or adjustable FPR? El cheapo/eBay FPRs are discouraged.

 

Did you say what injectors you're running? I'm on some Bosch browns at 3bar. Pretty sure they're over 300cc, maybe 350 or higher; Dave at Emerald chose them.

 

I'd perhaps revisit your injectors and fuel supply, and while at it flip the ITBs. If nothing else it'll be a decent experiment and a giggle.

 

Certainly seems like you know your stuff though. I'm in Peterborough if you fancy a hoon some time.

Edited November 2, 2017 by DrSarty

[welshpug 1,657]

A little birdie told me that Jenveys give a little more mounted 'upside down', i.e. fuel rail underneath.

 

This may be an old wives' tale, but if you feel like going back for another power run to try this I'd be very interested.

 

 

not possible without a manifold swap on DCOE pattern, but there is a science behind it, on a less inclined Longman inlet the injectors almost point at the port directly, like the original set do.

 

whereas the longer curved inlets dont allow this however spraying fuel into a high velocity pulse will draw it around the curve whilst hopefully mixing nicely to give a good bang in the cylinder.

 

a shorter that ideal inlet and not enough inlet advance can push the power peak up to the top of the rpm at the expense of torque, usually highlighted by the torque peak being high in the rpm as well.

 

not to say thats what is 'wrong' here, it looks like a curve very much like many mi16's

Edited November 2, 2017 by welshpug

[jackherer 543]

I've lost count of the number of 'experts' that see my Jenveys mounted upside down and tell me I am definitely losing power with them that way.