Offroad-Express

Just seeking input from anyone who knows, or has actually done work with n/a TD42. I will do anything to this motor except turbo it.

From everything I have read (all anecdotal on internet forums) the TD42's head flows pretty well, and the stock exhaust manifold is pretty effective, which leads to the advice 'chuck a 2.5" pipe on after the flexi'

My query comes in that the stock pipe is 3+3 into 2 into 1, and even when it's all 1 ("the collector") the OD on that pipe is about 2 1/4". I've read about scavenging and exhaust velocity and all that black-magic, without doing any actual measurements or calcs I say the stock manifold is restricting it, and that putting a 2.5" on after the flexi is a bit pointless when it chokes at 2.25" before it.
BUT I still wonder if I wrapped the stock headers to keep them hot and flowing, and did the 2.5" pipe from there, if that would be worth the time that could be spent saving up to have full extractors fabricated?

As to the EGT, I don't mind an averaged reading, so my thoughts would be to put it at the collector, but that's a good two feet away from the head and probably would give meaningless readings? I've been told that Cylinders 1 & 6 run the hottest and to put the probe 2-3" from one of their ports, not my preferred idea, but again, I'm seeking wisdom from those who have gone before.
Cheers all.

unless you change your mind and force feed it don't go expecting too bigger percentage gains in performance, the joker from trundles in taranaki who used to be on here has played around with those engines a lot and knows lots of tricks it wouldn't be a bad idea to google him and have a yak about what hes done to them to get good hp and torque figures, is it a factory LWB flatdeck there aren't too many of those around over here

if you're sticking to na i'd start with making a tunnel ram inlet manifold and look at some equal length extractors.
without turbo you are very limited to the amount of fuel you can add before egts get something to melting point.
so utilising any free energy you can that helps the engine scavenge air is imperative

keep in mind that to get increase in performance you need to add fuel.
extractors and inlet mods can help add some more air flow but usually only at a certain rpm range.
the problem is that mech injection is very difficult to increase the fuel at only that rpm range and not at other rpm points where there is not enough air flow. if your pushing it to the limits that becomes critical.

performance always comes from correct afrs timing and sufficient air to cool it.
i noticed with my na td42 a markable change with or without a snorkel and with facing the hat forward or aft.
if it were me i'd go smooth flowing snorkel decent airfilter and cut a couple long runner qd32 manifolds up and whip the log inlet off .
if you can sort the volumetric efficiency out in the inlet you'll have a reason to add fuel and the gains to be had are across the rev range of any td42 i know understanding that its still going to be most efficient at a certain rpm

Thanks for all the input.
I'm not so much looking to boost it, I'm more looking to de-restrict it.

I have thought about doing a twin-intake as well, maybe twin snorkel, with full size feeds to the front and back 3 cyls. (or am I better off feeding 1 3 5/ 2 4 6?)
Does anyone have a stuffed TD42 head I could borrow to jig up my ports?
I never really bought the hype about "ram" intakes, as flowing 12000 litres at atmospheric pressure... you'd have to be going mighty quick to have the ram under anything but vacuum! Interesting that you noticed the difference slidenyo.
I have a cyclone filter off an old mitsi 3 litre, which I think would have more filter surface than stock, but probably restricted in the pipe sizing :s
I'll have a look at some truck ones.

The story continues!

To derk, no, this was cutdown from a full body unfortunately, I would love to find a ute bench seat for it!

tunnel ram an v.e is very real man.
intake pulse is close on speed of sound so easy way to think about is valve shuts intake charge hits back of valve resonates back up runner then bounces back off manifold or passing pressure wave till valve reopens, hence tuned length runners trying to meet the pressure wave bouncing back with a valve opening.
the longer the runner the less bounces and the less diminished the pressure waves intensity ie boost for free

slidenyo wrote:tunnel ram an v.e is very real man.
intake pulse is close on speed of sound so easy way to think about is valve shuts intake charge hits back of valve resonates back up runner then bounces back off manifold or passing pressure wave till valve reopens, hence tuned length runners trying to meet the pressure wave bouncing back with a valve opening.
the longer the runner the less bounces and the less diminished the pressure waves intensity ie boost for free

Follow up question: What is the cam duration for the intake on a TD42?

think i googled it to be 240 odd degrees a while back.
your thoughts for splitting the manifold could work well with the firing order.
mate has a similar split manifold with a big holset and it goes bloody well.

slidenyo wrote:think i googled it to be 240 odd degrees a while back.
your thoughts for splitting the manifold could work well with the firing order.
mate has a similar split manifold with a big holset and it goes bloody well.

I didn't have any luck on the google. that's cam degrees not crank, aye? That's nearly 3/4 RPM... or I suppose half? that if it's cam degrees.
I really need a spare engine to work all this out on!

duration open on the valve for rotation of the cam as i understand.
then its a 4 cycle engine so cam is driven 50% of the cranks rotation.

slidenyo wrote:duration open on the valve for rotation of the cam as i understand.
then its a 4 cycle engine so cam is driven 50% of the cranks rotation.

Yeah, but with a number like 240 I'd expect that is crank degrees (180+ 30 +30) for BTDC to ATDC, unless I'm missing something? (I probably am!)
There was a really good diagram I'll try and find it again.