how to win power on 4.2l non turbo (85kw) GQ patrol

Hector Robles
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Joined: March 4th, 2016, 10:26 am

how to win power on 4.2l non turbo (85kw) GQ patrol

Unread post by Hector Robles » March 4th, 2016, 11:39 am

Hello everyone,
I decided to post this topic cause i just finished to restore a Nissan patrol 4.2D (without turbo) from 1989 and 197 000km, is the first time i work on a 4.2
I'm use to drive a 2.8TD from 1993(european version).
After 1 week test i'm a bit disappointed, it have a good torque and the gears are much longer (than 2.8) but the engine feel really smooth and do not respond well. :zzz:
The torque is great, but i would like to win some additional power. :)
Did some one know good tips to win a bite of Kw?

-Of course the best would te to install a turbo system kit but 3000$ i the price i paid for the truck :lol: ... 2LT/pd.php

-i'm thinking about taking away the silencer, and put a glass pack, but i had a bad experience by taking it away on 2,8Td, the ... the turbo pressure drooped down to 0.6B and loose even more power. :lol:

Sorry for the good grammatical falts, i'm writing from South America!

thanks for you attention

Peter Aawen
Posts: 20778
Joined: June 17th, 2005, 8:01 pm

Re: how to win power on 4.2l non turbo (85kw) GQ patrol

Unread post by Peter Aawen » March 4th, 2016, 1:11 pm

While a free flowing exhaust & better extractors/headers can give you a little bit of extra power from an N/A TD42, there really isn't much in it..... :( While both the N/A TD42 motor & the RD2.8 motor were both 'rated' to have a flywheel output of 85kW, in bog stock straight from the factory condition & running 7.50R16 or 33x10.50R15 tyres, a brand new N/A TD42 in the late 80's early 90's would be really pushing to show much more than 50kW at the rear wheels on a dyno - I suspect the RD2.8 was similar, but they were engines designed to develop torque rather than power; the TD42 had scads of torque from 900 rpm right out to 4200 rpm, while the RD2.8 needed the turbo to be spinning & the revs up around 2500 rpm (which is why they had a Dual Mass Flywheel & a clutch that needed a sensitive driver to get the best from them!) BTW, even with an N/A TD42 tuned to its absolute utmost 'stock' power output but still running only stock the stock pump & injection gear, you might be lucky to get 55kW at the rear wheels!!

The 1989 TD42 is a 'less refined' motor than the 2.8Td & far less reliant on proper exhaust 'tuning' to develop the power it gets, (nothing beats cubic inches for plain grunt!) unlike the small & highly rev/turbo reliant motor that the 2.8 is; so fitting a less restrictive exhaust shouldn't be a major issue with the TD42, but without a muffler of some sort, it will be noisy!! When we were running N/a motors in our fleet/Tour vehicles, I dropped the tailpipe resonators & fitted 'turbo' mufflers under the cab in a 2.75" dia exhaust with similar dia tuned length extractors replacing the cast iron exh manifold; and after tuning the I/p to suit the changes in breathing, it made a (just) noticeable difference in power & a slight improvement in fuel economy (read = to maybe 52kW instead of 50!) but it really wasn't much of a noticeable improvement & it wasn't really a cost effective change in the long run.

But fitting a 'soft blow' Schweitzer turbo with a 3" exhaust flange, dump pipe, & a straight thru (no muffler at all) exhaust made a massive difference to driveability (once the I/p & injectors were set up to match the extra air flow - & btw, just winding up the fuel is NOT the thing to do if you want power AND reliability/longevity!! :eek:) a noticeable improvement to power output (85kW at the rear wheels wasn't uncommon, but also wasn't the maximum achievable!!) and actually improved the fuel economy too (when you drove it the same way as you drove the N/a - altho it was easy to use the extra power all the time... :o ) The investment in the turbo's, while a bit expensive up front, turned out to be a very cost effective mod; they paid for themselves in less than 12 months/about 100,000 km of much nicer driving & towing. Honestly, if you want more power from the 4.2 diesel, you'd be wasting time & money to do anything else, altho you do also need to get the I/p & injectors 'tuned' to give you the best balance if power/torque & fuel economy without making the engine Exhaust Gas Temps go thru the roof & make the engine over-heat a lot & become very un-reliable!!

I used the Denco Turbo kit with 3" exhaust, ( ... -upgrade-3 is the one, I think?!) but after trying one of those for a bit, got them to upgrade our kits with a larger dia turbo outlet flange to match the larger dia exh pipe - the std outlet flange was just a little too restrictive & pushed the EGT's too high too easily; once the more open flange went on the EGT's never went over 550 deg C again, so I guess there was a bit of scope for more power.... but it certainly wasn't necessary, & a couple of the Patrols we ran travelled more than 1 million km after fitting the turbo with basically only the scheduled servicing - & I can't argue with that for reliability! I'm now working on taking the latest one that far too!! :thumb:

So don't waste time or money playing around with anything else, it isn't worth it in the long run - get a good quality low boost turbo kit & free flowing exhaust fitted & get the I/P & injectors 'tuned' to work their best with the better air flow in & exhaust flow out! You'll be glad you did in the long run!! ;)
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