Mighty results from big bore, injection timing adv

[mudgrip4]

Last year had the injection timing advanced and fuel delivery increased on my 88 bighorn 4jb1t - big power increase. Last Thursday fitted a 2.5" big bore - even more power. Today took vehicle round to be dynotuned and to check power increase...... WOW!

Horsepower rating for 4jb1t (from several Jap websites) is 110hp or 81.5 kw for non intercooled, and 115hp and 84.5kw for intercooled motor. These measurements are taken at the flywheel, and the tuner told me 4x4s lose about 30% of this power by the time you go through the gearbox, driveshaft, rear axle etc. So non intercooled should produce about 77hp at rear wheel.

Knew mine has alot more hp than some other 4x4 makes but we all got a serious shock with hp figures. His dyno machine factors in and adjusts for diff ratio, and he said it is a conservative dyno reading, accurate to within 1 kw of manufacturers specs with new cars he dynotunes.

He set it up and the first reading was an amazing 103.4hp at the back wheels. Then proceeded to adjust and readjust for more fuel up to point just before it began to smoke - when power began to fall off - and we finally set the fuel tuning at what we figured was optimum, and the reading at this final point was an enormous 116hp (85kw) at the rear wheels.If you add the 30% power loss through the drive train, this equates to around 150hp (approx 113kw) at the flywheel. Or an increase of 40hp from standard. Torque also increased from 219 to 241.8 ft/lbs ( or 325nm).

This tuner does quite alot of race cars/performance cars(Porsches etc) and also alot of 4x4s. Said the 4.2 6cyl Nissans ( don,t know year) read about 106hp at rear wheels, and the new 3.0 Prados read about the same as my bighorn - round 115hp which accounts for the fact I easily had more power than a heavier Prado coming back from the mountains yesterday.. Also said some 4x4 models don't respond over well to bigbore, but for some reason the Isuzus do.

So a serious power increase is possible - as reported from aussie club members. And oh boy this little buggy goes now. Top speed about the same (30.5" tyres) at round 150kmh, but acceleration hugely up. This is now fun to drive on road and has absolutely huge grunt off road when pointed up hills- takes off like a rocket in low ratio.

Chch tuner Blackwood Motors - phone [phone]. Cost for dyno check and tuning - club price - $157 incl GST. Well worth it. A very grunty little vehicle!! This rocks. Email me if anyone needs more info - Mike .

[Stu]

Awesome results mate. Just as a matter on interest, how are Deisel engine checked to make sure the Fuel/Air ratio is correct? Do they use a wideband o2 sensor like with petrol engines? Reason I ask is my own car is getting tuned later this month and as I've hired the dyno for the whole day might get dad to put his Bighorn on for a laugh. I've got a wideband to use so could do alittle tuning on the Bighorn if thats how its done.

Cheers.
Stu

[mudgrip4]

Can,t tell you about fuel/air ratios, o2 sensors etc. My main purpose was to put it on the dyno to assess horsepower, and because I suspected it was running too lean - too little diesel getting through - we simply screwed in the fuel increase screw in small bites. Gave it a bit more fuel, tested on dyno, and repeated this process about 5 times. Result 12.3 hp gain simply from more diesel. The other massive gain from the overall performance tuning I've done has been torque increase. Standard 4jbi-t has 225NM of torque and mine now has 328NM - about 47% increase. Full torque at 2308rpm, full hp at 3320.

Hp curve dropped off fairly quickly after 3320rpm and not much happening after 3500rpm. Power now kicks in earlier - from 1500rpm, and is pulling hard by 2000rpm.

Advancing the injection timing a little - not until it rattles - and at the same time increasing the fuel delivery gave the single biggest increase. The bigbore extended the range to 1500 - 3500rpm and added power, especially early (say 1500-2300rpm), and the dyno adjusted fuel flows to precisely meet the changes the bigbore had brought to the motor.

Any good diesel shop can do the small advance in injection timing and this should cost no more than $80 - 100. Needs more fuel with this, so people can try a half turn inwards at first on the fuel screw, then give the motor some revs and either add more fuel or decrease it in small increments until you arrive at the point just before it starts to blow heavier black smoke. This on the dyno was the point of maximum horsepower - once into the black smoke the power dropped off.

And of course its great fun because it now sounds like an Austin Healey when you put your foot down. Good luck - Mike.

[dani4JB1T]

Aloha
that tips it sound great, I`ll do it too...hehe

One question: What is your new fuel consumption ¿?<br><br>thanksss
Dani

[mudgrip4]

After the injection timing advance and extra fuel tune I monitored consumption for several months, and with light use of the right foot I averaged 52km per gallon or 32 mpg. This is changing gear at maybe 2300 rpm rather than using the turbo alot and involved 50-60 -80kmh zones in and out of city which probably give optimum figures. Open road drops to about 50ks or 30mpg. Haven't had time to check bigbore influence but general advice is slight increase in fuel economy. Having trouble at the moment keeping foot off gas as its lots of fun using 328nm of torque and 150hp! Will try hard to be restrained and get some economy figures....maybe in a couple of weeks....Mike.

[geeves]

Air fuel ratios dont apply to diesels except if you are pumping in far to much diesel which would be obvious. Diesel engines always use max air

[mudgrip4]

Just confirming that - spoke to dyno man this afternoon and he says O2 sensor and air/fuel ratio tuning not relevant for diesels except as Alan notes. Commented that autos generally lose 22-25% hp by time it reaches back wheels, whereas 4x4 manuals lose 25-30%, with 25% a conservative estimate. So hp at rear wheels is approx 3/4 of flywheel hp for us. Question - are we continually running through the transfer case, as with the gearbox, or only when 4wd engaged. Will there be difference in power loss between 2wd and 4wd? Mike

[mudgrip4]

For Dani4jb1T - have just had chance to assess fuel consumption after significant power tuning above. 2.8 bighorn swb used to do 52ks or about 32mpg. Since tune now does 48ks or 30mpg = 5-6% loss, though this may be due to my heavier right foot - extremely worth while.

Just looking at two other smaller tuning adjustments inside the diesel pump which a friend tells me have given increased fuel delivery, more low down torque and better acceleration and top speed.I'm no mechanic and have never been inside a diesel pump but see what you can get from this description.

First adjustment is to remove top of pump, mark position of plunger/rod and turn plunger with the rod on it to allow rod to drop to greatest depth in its housing.Second adjustment - under rod is a star wheel type cog (ratchet?)- mark position again and turn from from 12 to 6 o'clock i.e. half a turn. Both allow pump to run richer, adding 5-10hp for my cobber's isuzu.

There may be something in this as after the injection timing advance and initial fuel increase adjustment on mine, the pump actually leaned itself off and I've had to reset it for more fuel. My mechanic tells me he has come across this before. It may be the plunger/rod and 'star wheel cog' beneath it are preset to run at a leaner level than the needs of a tuned up motor requiring more fuel.

Will chat with my tuning mechanic tomorrow on this - but would welcome any thoughts - Mike A.

[mudgrip4]

Spoke with diesel tuner today re above in-pump adjustments and he says they will boost fuel and performance but same effect in his opinion is achieved by adjusting external fuel delivery increase screw - which I've already done. Perhaps the two in-pump adjustments can be tried if the pump keeps leaning itself off so it is reset to handle the extra fuel resulting from the fuel delivery screw increase? Mike.

[James W]

I thought the two methods sound the same, but I wonder what happens at zero throttle?
It would be desirable not to change this setting. Perhaps this is the subtle differance?

[mudgrip4]

Yes. Not overly keen to alter in-pump settings at present as fuel screw increase still doing well for me since last dynotune. Will follow progress with my cobber's 2.8 with the in-pump adjustments. See what goes. Or blows... Mike.

[James W]

Mike - did you have to back off the idle adjustment to get idle back to what it was after winding up the fuel?
I would expect the idle to rise?

[mudgrip4]

Yes - dropped it back 100-150 rpm from about 950 - Mike

[namic69]

I am living in Auckland at the moment. Can anyone recomend someone here to advance timing and fuel rate?

[namic69]

Mine is the 96 Bighorn with the 4JG2 Motor

[Bruce]

As I've said in previous threads, I have been doing some reaserch on this matter. Found an interesting article on a site today. www.lcool.org/technical/elec_diesel_tuning.html
It is mainly to do with electronic diesel tuning devices, but does reflect on manual diesel pumps. The one thing I read with interest was when the fuel rate is increased it contaminated the oil much quicker there for oil and filter changes need to be done at 2500k's instead of 5000k's, can become quite expensive I would think.
The article is quite a big read 10 pages but mainly to do with electronic devices. Hope this may be of help to anyone who has done the tune up or about to.
Cheers Bruce

[Jimmu]

Excellent results.

I am about to start some mdifications for some extra grunt.

So your experience is very helpful.

Jimmy.

[Jimmu]

With the Big Bore exahust. Is that 2.5" Maundrel bent or standard?

Did you get the dump pipe done as well?

Is 3" overkill?

Jimmy.

[adam]

i have been told that 3" is optimum for 14-15psi boost

2.5" will restrict it a little, however from what i have read on the net, 2.5" is fine.

mandrell bends are the best, as our turbo manifold provides all the backpressure we need for low down torque, past the turbo you want to get the gas out fast as possible.

that said, a 3" press bent will be fine.

even a 2.5" will be fine.