V6 3.0l Performance Mods

[kev500sa]

Hi All,

I am new to this formum. I've had a NH 3.0l V6 for the last 3yrs, done about 260000km, due for an engine rebuild. Been looking for the best upgrade. Got hold of RPW, they recommend the following: Stage 1 cams, rebored throttle body and plenium, free flow exhaust, extractors and a piggyback ecu. Anyone done the same? Does it make an improvement?

Thanks,

Kevin.

[-Scott-]

RPW have been around for a few years now, so they must be doing something right. However, in my only attempt to deal with them, I wasn't impressed.

In my experience, they're all about extracting power, and they seem to be successful. But, I believe the 3.0V6 is inherently lacking in low-down torque, and I wouldn't expect RPW's package to help with that.

How do you use your Paj? If it's mainly touring and/or beach running, more power but less torque is probably an acceptable compromise. I'm more interested in low speed performance in the rough stuff, so I'm in no hurry to buy an RPW kit.

[FrankR]

Got hold of RPW, they recommend the following: Stage 1 cams, rebored throttle body and plenium, free flow exhaust, extractors and a piggyback ecu. Anyone done the same? Does it make an improvement?

Of course they recommend those things - that's what they sell.

The cams probably increase upper rpm power at the expense of the bottom end of the torque curve. Before buying those, I'd want to know the cam specs. It's easy to lose drivability with the 3.0L, due to one change impacting other parameters that are tuned by MMC for best all 'round performance.

I'm now playing with Diamante cams in my 3.0L, but have found them to make for a big top end at 4000rpms, but a lazy engine when installed straight up with a C/L of 115° since the torque curve starts at 3000 rpms. I'm now rolling them forward to 107° to see if I can move the torque toward 2500 rpms - which should work better with the gearing - particularly in O/D.

In fairness to the cams, I have made other changes to my engine that favor the upper end - mild head/exhaust manifold/lower intake manifold porting, custom upper intake plenum which eliminated the long runners, 2.5" exhaust, etc.

You might be happy with a fresh 3.0L - actually quite good until large tires are added, but if you want more power from it, AFAIK there's only one solution - blow in it:




Frank

[kev500sa]

Hi Scott, thanks for the reply. I use the Paj for work. I build roads in Africa. Last job was in Botswana, lot of sand. Now in Zambia, lot of potholes. Do about 50/50 off road and long distance. Get average of 7l/100km.

RPM advised a 267 cam (stage 1). The cost of rebuilding will be $5k. I don't want to modify the motor too much due to reliability and servicing. However I do want to put 33" tyres on (got 29" now) mainly for ground clearance, so need the extra power.

Frank, your supercharger looks great!!! just too complicated for me here, plus I have a Toyota LDV that I put on turbo/intercooler, I have rebuilt that engine 4X (330000km).

I find that the Paj seems to hit a powerband at 3000revs. Thought it was the oxygen sensor, put a new one in, same problem.

My plan with the rebuild is to rebore the block and put in oversize pistons to give more lowdown torque.

Thanks again for your repllies.

Kevin.

[-Scott-]

OK, based on that, I'd look for a little more capacity & a little more compression (not too high - maybe 10:1 tops?), balance it all and bolt it together carefully. I would NOT lighten the flywheel - but you probably already know that.

I have a 2.5" exhaust on stock headers, and feel it's a little too big for a stock motor. I'd suggest rebuild and try it with the new cams before you do the new exhaust - reducing backpressure can have the same effect as increased overlap, which is great at high revs, but not so great just off idle. Any idea how the new cam overlap compares with stock?

[kev500sa]

Hi Scott, they say the stock cams are 182, lift 0.394. The RPW stage 1 cams are 258 with 0.360 lift. I already have a free flow exhaust with stock headers, K&N airfilter.

If I increase the compression ratio (skim the head), will that not affect the clearence on the valves? and also increace top end performance only?

Cheers,

Kevin.

[-Scott-]

Hi Scott, they say the stock cams are 182, lift 0.394. The RPW stage 1 cams are 258 with 0.360 lift. I already have a free flow exhaust with stock headers, K&N airfilter.

If I increase the compression ratio (skim the head), will that not affect the clearence on the valves? and also increace top end performance only?

Cheers,

Kevin.

Yes, skimming the head will affect clearance to valves and also affect cam timing. I was thinking more in terms of finding aftermarket pistons - you were planning on replacing them anyway, so I was guessing you'd be able to find something which will increase compression without skimming the head. Did you discuss this with RPW? Worst case, have pistons notched to clear the valves.

Compression alone doesn't determine where peak power will be achieved - look at a diesel engine. High compression engines can produce good bottom end torque. Most high compression engines don't, because they're designed to produce high top-end power. This is typically achieved with "big" cams which allow the cylinders to fill quickly at high rpm, but these same cams typically don't work as efficiently at low revs. There's always a compromise somewhere.

[FrankR]

they say the stock cams are 182, lift 0.394. The RPW stage 1 cams are 258 with 0.360 lift.

Their information is wrong. Here are the Gen1 3.0L cam specs:


Intake open = 19°BTDC
Intake close = 59°ABDC

Exhaust open = 59°BBDC
Exhaust close = 19°ATDC

Intake Duration = 258°
Exhaust Duration = 258°

Intake C/L = 110°ATDC
Exhaust C/L = 110°BTDC

Lobe Separation Angle = 110°

Valve Overlap = 38°

I did not measure maximum lift,, but I did notice it to be above .350" and but below and closer to .400" since I just degreed my Diamante cams which have the same lobe lift as the Montero. You will likely penalize yourself with less lift.

The FSM suggests a limit of .008" maximum milling head and deck combined. You could go more, but your non-interference engine could become an interference engine with stock pistons. Milling of the deck and/or head will change your cam timing, so if you want peak performance, be prepared to install eccentric cam bushings or locate the RPW SOHC adjustable sprockets.

Compression increase will give you very little power gain - 1 point on a 3.0L is good for about 3-5HP maximum, but throttle response will increase somewhat - as will your fuel bill. Here's a calculator for you to see:

http://www.bgsoflex.com/crchange.html

Also, a .020" overbore will only give you a CR increase of .1 - good for a whopping 0.4HP gain.

http://www.straightline-perf.com/crcalculator.html

Perhaps you'd like to build a stroker 3.0L?

http://www.importperformanceparts.net/

Anything other than increased CID or forced induction is probably a waste of money if noticeable gains are expected.

Good luck,
Frank[/url]

[NJV6]

I remember Frank (bitsamissin) doing some dyno work on his and he got something like 20hp extra. Might try and find it - if only the search function wasn't fawked!