S1600 Mi16 Racer

[Hexer 1]

Hello all, we have a nice engine and car here, long list of parts but some lack of power.

 

Dont get me wrong, it works, no problem with reliability, hitting 9000rpm, has some 11000 miss shifts also... built as is should.

 

Torque is about right with the short stroke, if it would keep the figure till 9500 the power would be over 210 but its not the case.

 

Parts:

Ross pistons, dome high as normal plugs wont work, just racing ones

Aluminium rods, half the weight on the piston end ad steel...

Stock xu5 crank balanced

Catcams in the head, solid lifter 298/282 at 106/110

The head its not ported just the surface is cleaned polished

Ferrea 6mm steam, stock head size

Jenvey ITB (needed some after work to fit right...)

Pace dry sump, best choice, all the lubrication problems the XU has have disappeared, after a year of racing the bearings are like new.

Running on 102 octane race fuel.

 

At the moment it has a 70mm exhaust, last year it had a 60mm, no real change in max power, but its more consistent. Header is the same size as the 309 but straight.

 

 

If anyone here has some idea where the power is hiding please share

[Biggles 65]

What's the exhaust manifold ?

[welshpug 1,657]

hard to say but the inlet looks far too short, ports probably too big also, hence silly rpm peak.

[Hexer 1]

Manifold is a 4-1 primary 650mm and 42.8mm in dia and a decent collector, not F1 but its fine.

 

We had a a longer one (90mm), but at the last dyno we changed to the shorter (45mm) cos it gave 7 hp plus and lost 0 torque, we tried a shorter (30mm) one but that was loosing 15Nm and no power gain.

 

Ports are not changed, like maybe 0.5mm bigger than stock cos the casting was cleared off, the valves are 0.2-0.5mm smaller than stock, the head has problem at overlap, stock like max 2.5 ex and 3.5 in and after that they get to close to each other, so we placed the intake 0.5mm deeper and the ex 1mm deeper than stock plus no oversize to have plenty space for dyno tuning. Anyway the intake runner and valves are a lot bigger than any competitor engine in the 1600 class, so if we loose some with torque we should gain with power...the problem is that this is not happening...

[Rob Thomson 6]

You need a proper modified head.

 

Surely a virtually standard head doesn't have sufficient flow for 210 bhp. They're good, but not that good.

[Hexer 1]

As size the mi16 is a lot bigger, bigger than a TU ever could be.

 

Valve size:

in- 34.6 vs 31.2

ex- 29.6 vs 24.6

 

The same is true for the intake runners. The valve angle is big, port is a bit low, its typical for the 1st gen street 16v engines (f7r, c20, fiat and the rest), but it shouldn't make a huge difference, it should have some nice flow figures.

[welshpug 1,657]

You need a proper modified head.

 

Surely a virtually standard head doesn't have sufficient flow for 210 bhp. They're good, but not that good.

yes they are

 

this is a 1600 too, with a head from a 1905 and 1998 cc engine.

 

im running similar peak power (200ish) from 1998cc with std head and 7.5k.

[Hexer 1]

yes they are

 

this is a 1600 too, with a head from a 1905 and 1998 cc engine.

 

im running similar peak power (200ish) from 1998cc with std head and 7.5k.

 

Yes, i'm running xu9 head, xu10 should have the same runners but bigger valves.

And also this is my concern, where are my ponies hiding...

Dont know if I'm missing something or we have some problems with the cam selection, maybe internal vibration...maybe the dyno

 

We made 168hp with stock TU head just biggest hydro cam and springs, and 12:1 pistons, stock intake and just a 60mm cat-back.

[Anthony 1,003]

Are you just running a single bank of injectors?

 

Given the high peak rpms, a second injector bank further out in the trumpets or even the airbox should likely yield some gains.

[Hexer 1]

Its single but 10cm from the oroginal spot.

[petert 586]

Not sure what 298/282 means, but for that sort of RPM you should be on 102/104 centrelines. What CR? It needs to be >12:1.

[welshpug 1,657]

the duration and timing don't match anything Catcams list directly, these two are the closest, and indeed timing is different.

 

these two are very close but one opens sooner despite the advertised duration at 0.1mm 298/290

[petert 586]

All toys. You need something similar to a Cosworth BDA profile, eg BD4/L1 combination. The intake needs to have at least 260 deg @ 0.050" lift, which would push the total duration past 320 deg. If running two BD4's for example, you'd start them at 102/102 and adjust from there on the dyno. I'd still keep the exhaust smaller (eg L1 type) because the Mi16 exhaust port flows too well for its own good.

 

http://www.camshaftshop.com/products.php?productid=855#specs

Edited April 22, 2015 by petert

[Hexer 1]

intake 298: 4901552

ex 280: 4901551

 

the ones I have intake opens 260 at 1mm.

if anyone is familiar with this head knows its impossible to run it at 102 degree, with big cams you need to sunk the valves hard to manage this.

102 degree with thees cams intake will be at tdc ~5.5-6mm and opening really fast, ex around 4.2-4.5mm, need extreme valve pockets on the intake side so you loose a lot of CR, and that's a problem with big bore and short stroke.

 

the BDA profile with the 322/261 and 11mm lift has the around the same under curve area as the catcams 298/260 and 12.5mm lift. With long and slow cams I'll loose torque.

yet you are right with the small exhaust, its interesting that its no need for a big exhaust cam.

[Hexer 1]

stock valves with stock head max opening is 3.2mm in and 2.3mm ex, and there is less than 0.8mm between the valves at that point.

 

we have over 12:1 cr.

[petert 586]

I run 3.5mm/2.5mm with 36.5/30.0 valves. I can assure you the valves are sitting as high as I can get them.

[Hexer 1]

did you measure at the gap between the in and ex valves?

 

Ps. catcams maybe have a new profile with 308 at 0.1mm and 275 at 1.2mm, that's an aggressive one, but good for power and in the same time keeps good torque at lower rpm. problem is the small base circle the xu has...

 

anyways, with a cams what we have it still has to go over 200hp.

[petert 586]

Never bothered to measure. There's been plenty of others with bigger setups than mine. It's been running non-stop for eight years now.

 

I run 33mm buckets to help overcome the base circle issue.

Edited April 27, 2015 by petert

[Hexer 1]

yes, I need bigger buckets also cos on the exhaust side is already a bit loose, the side support for the buckets is week on that side and with big cams it deforms, while the intake is perfect.

 

then again...where is my power? with lot less stuff i get to 200hp on different engines.