4JB1T Performance increase with a 2.5" Exhaust

[Jimmu]

Here is what theory looks like on a dyno sheet:



I should be wheeling that weekend if I am in town. Maybe we can get some old schoolers out to play hey Pissy, Frank, Bruce and Dave (Even though he drives a ford)

Jimmy

[geeves]

Im assuming this dyno measures at the wheels so add 25% for a true reading. ie about 80kw
at 3300 this is a good result but peak horsepower should be at 3800 suggesting you might still have some air restrictions to take care of. What mods have you done to the intake ie snorkle, high flow filter (k&N or unifilter) I dont know what the Rodeo intake looks like but the bighorns factory intake was diabolical meaning that a snorkle shortened the intake by a third and increased its size by double result roughly the same as bigger exhaust.
The good thing aabout modding the airflow to get more power out of a diesel is that unlike boy racer mods on petrol cars fuel use does not go up If anything it goes down providing you drive the same way.

[Dayno]

Well with the Rodeos the factory filter box is in the bottom right corner of your engine bay. The custom Snorkel actually made my air intake 2x as long as without. So what i ended up doing was ducking down to supercheap and picked up just some cheap arse 30$ POD filter and then to the steel shop and picked up some 3" and 2.5" steel pipe and made an adapter with a bracket on it which, when i removed the old filter box left 3 bolt holes so i simply bolted the bracket which i welded to the pipe into the existing holes and connected the factory flexable connect pipe to the end of the custom pipe and presto a new less restricting intake. (I left the snorkel on and placed the POD filter next to the snorkel pipe inside the engine bay to suck in cool air from outside) The only issue is the pipe is alittle too long and does bunch up the flexi pipe alittle.

[Dayno]

[geeves]

So far so good. It might be a good idea to build a new airbox to fit round the filter and reattach the snorkel. This will be better for dust and water. Another way would be to have a look at the filters on the Simota website. They have an enclosed pod that will save having to build the airbox

[Jimmu]

Can you throw up a shot of the snorkle from the outside? I was thinking if plumbing mine with down pipe too.


Jimmy

[mudgrip4]

Have just been given a mandrel 2.5" dump pipe to reach from turbo down to flexi for my 2.8 so will fit that next week and see what the difference is. Has to be a help.

[mudgrip4]

Dayno - I'm not convinced by the dyno chart above for your truck - doesn't seem right to me. A 54.6 kw result at the back wheels is only about 73kw at the flywheel, or about 100hp. This is not right for a tuned 4JB1T. It is the kind of result you'd get for a standard motor - even a little less then the 110hp standard for a motor without intercooler, or 115hp with the i/c.

Did they test after the diesel pump had been advanced etc. If so, the truck should be up round 80+kws at the rear wheels as was mine, and jimmu's above. And it should be pulling very strongly now - a big difference in performance - much more low down torque and much quicker right through.

I wonder about their dyno's calibration. Your stats should now read like jimmu's.

If you can link up with jimmu - get him to drive your truck for a tuning comparison. Your 54.6 kw after tuning is not right somehow. Even my latest truck with part of its tuning done would now produce alot more kws than that, and shows a big performance increase with pump timing and diesel increase done, and bigbore fitted from the flexi back.

Mike.

[Dayno]

Here you go Jimmy, Sorry about the glare. It's 4 in the arvo so i have the sun facing directly on my driveway =/.





@ Mike - I have no idea how it was done as i wasn't there, i went to work and left it in the hands of the mechanics, and picked it up after work, so i can't tell you exactly what was done. The TF Rodeo's arn't intercooled sadly, i think the TDI models are 96 up? honestly i wouldnt know too much about the newer models as i couldnt afford them so i only reasearched the TF's witch are just standard Turbo Diesel.

@ Jimmy - Im really interested in seeing just how much power i can atain from the 4JB1T and just how much my Rodeo is lacking currently. If you are free next weekend (Anzac Long weekend) im all for going on a trip or even just a day cruise soemwhere. Not too mention would be great to have a yarn to ya about general 4x4ing and too see which parts from the MU's would fit in the Rodeo. (i.e Intercooler)

On a side note, Last night was thursday late night, so at my mates usual meet up, we decided to go race at the local drag road (just an unused road with 2 lanes in the middle of no where) After talking up my ute, i was forced to drag off a 98 v6 3.5 pajero, we were tied up the road until about 3rd gear then he smashed me =(. So it does have decent power however if i could get more around 80kw im definantly interested in anyway i can acheive this. (aside from the obvious ,intercooler,bigger turbo etc)

[geeves]

To stay with a v6 pajero to about 80kph (end of 3rd) is a good result I think your dyno is telling lies

[mudgrip4]

Fitted a new 2.5" dump pipe to my truck from turbo to flexi (about 15-18") and tested it. I find it definitely has a bit more low down torque than before, which makes it easier and less rev dependent to drive - esp down low off the lights. Now pulling a bit harder up my favourite steep hill from 1500rpm.

Performance on the stopwatch after 2500rpm in higher gears appears about same as before - though also seems to have a little more power up top as well.

In summary - for my truck only and its press bent 2.5" main pipe - the addition of a 2.5 dump has added some useful down low power - helpful for accelerating and for offroad climbing. It has proved a useful mod because the new piece of pipe was given to me - but not a necessary mod. The earlier addition of the 2.5 main pipe from the flexi gave a far bigger addition of power and torque. An ok addition for say less than $100.

This doesn't negate jimmu's report of bigger power increase. Rather my longer lwb press bent main pipe, as opposed to mandrel, may be the factor limiting more gains.

Quite happy now with new truck's performance - this one not as quick as my last 2.8 swb which was a regular hotrod at 155hp. 80-110ks in 6.4 seconds with 30.5" tyres. But in comparison this one feels like about 130-135hp, and this extra bit of tuning and horsepower makes it now a strong and enjoyable truck to drive. Still a tad more hp to come from snorkel and K&N, but enough power now to push new 33s in next couple of weeks.

[Dayno]

geeves said:

To stay with a v6 pajero to about 80kph (end of 3rd) is a good result I think your dyno is telling lies

If that were the case id be happy however i ment until 3rd gear which while i was winding up he pulled away. also 3rd gear 80k's? my diff must have a diffrent ratio because 3grand in 4th is around 90 - 95ks im pretty sure. Also im running 29's so that may alter your comparison alittle.

@ mudgrip - Thats good too know you gained something from it, what i would be dissapointed on, is if it did nothing to increase it at all. however im sure a 2.5 pipe pressed exhuast wouldnt create that much of a restriction for it to not be compared with a mandrel bent one (however of course there is still some minimal restriction). But im sure we can agree on one thing, And thats that, if you reduced the restriction from the turbo back via a larger pipe, even if it is only a small amount you will still gain some power. however the question remians, Is it really worth it?

[geeves]

3 grand? Rev limiter is at 4200 Useful power is all the way to 4000. I use mine all the way to 4000 if I need to

[Jimmu]

Thanks for the pics Dayno. I have a snorkle already but the pipe from the snorkle to the filter is average at best.

The standard power on his truck is about the same as mine was pre tune so I do not think it would be that far out. He may also be running leaner fuel ratios and he is only running 14Psi.

There is plenty of room for increases if he wants to push it further.

I think it is confusing to quote flywheel HP as it is not possible to measure with any accuracy flywheel power, short of pulling out the engine and running it on an engine Dyno.

A 2.8l 1993 MU is quoted as having 108Hp (81kW) at the flywheel. On the Dyno mine had 66HP ie a 39% loss based on the spec sheet. If you try to apply this loss in reverse to my new figures of 100Hp at the wheels you could argue it now has 163HP at the flywheel.

I don't for a second believe it has anything like that kind of power.

Also keep in mind that wheel size makes a noticeable difference to power figures on 4wd's because of the massive increases in weight big rubber brings. Francesco got 101HP or so running 32" muddies out of his 3.1. With 29, 20 or 31 he would have pulled bigger numbers. I was running 31's when I did the tune. With the 33" mudders mine would run less than 100HP I am sure.

The Dyno tuner who did mine does alot of race trucks. The most power he has seen out of one of these engines is on a rodeo with a front mount and a 3" exhaust running 25PSI make 127HP at the wheels.

While more power is always good I would rather not have mine pop in the middle of Frazer Island... again...

Jimmy

[mudgrip4]

The outfit that dynoed my first truck does alot of race cars as well as 4x4s. He said to expect 25% power loss from flywheel to back wheels. Sometimes 30% in some older autos. Several good sites quote isuzu power specs ex factory as 81kws or about 109hp (110ps) for the non i/c 2.8.

On this basis jimmu, your 101hp at rear wheels equates to about 135hp, not the 163 you mention - and that is entirely reasonable. My swb showed 85.5kw at the rear wheels which is about 114hp at the wheels or 152hp at flywheel. After this I added the K&N which gave it another 4-5hp when clean.

Variation can happen when testing with different size tyres on rollers. When dynoing mine however, the guy removed the wheels, entered the diff ratio, and assessed it without rollers. He said he has found the system to be within 1kw of factory spec for vehicles he has tested.

[Dayno]

I think that you guys seem to be missing the big picture here, I am not going down a 1/4 mile track with the Rodeo, I am hill climbing/smashing through sand dunes and towing either my camper trailer or a work trailor. Therefore speed off the mark and top end speed up and over the gateway bridge (which i went over today and the second bridge is really coming along fast) is of no relevance to me. All im chasing down is getting as much torque as possible to accomplish what my mates 4.0L Falcon Ute cannot. Today i went to the gold coast to pick up a EA Falcon padock basher, to transport it back to my home town my mate said he will use his 4.0L V6 Falcon Ute to pull a 1 1/2 ton car trailor all the way there and back with the car. (car added at least another ton to the weight of course) so roughly he was towing 2 1/2 tons of dead weight through all the sets of traffic lights, stop start stop sart stop start..... he had to rev his ute to 4 1/2 grand to get any real pick up. Now i asked him how many KW he has and i believe he said somewhere around 150kw (exact number i wouldnt know) now, if my Dyno reading says my Rodeo only has 54.6kw yet has more Torque then my mates Falcon ute, Then my goal has being reached. All im after is the power to pull heavy loads and still be able to go over hills without having to rev the "you know what" out of my engine causing it to overheat over long distances, not race down a 1/4 mile track.

[Jimmu]

mudgrip4 said:

On this basis jimmu, your 101hp at rear wheels equates to about 135hp, not the 163 you mention - and that is entirely reasonable. My swb showed 85.5kw at the rear wheels which is about 114hp at the wheels or 152hp at flywheel. After this I added the K&N which gave it another 4-5hp when clean.

That is my point, % loss is an estimation.

Mine only pulled 66Hp at the wheels stock. So based on the 108Hp I had a 39% loss from the flywheel, not the 25% quoted. (Assuming mine made stock power)

This is why people compare power at the wheels.

mudgrip4 said:

When dynoing mine however, the guy removed the wheels, entered the diff ratio, and assessed it without rollers

Sounds like a hub dyno? Like a Dynopack dyno? You cannot compare figures from a hub dyno with a roller dyno. Hub Dynos always read higher than rollers as there is no tires to push.

It does not make my figures right, or your figures wrong. It is just different and as such cannot be directly compared.

Jimmy

PS My truck pulled less power in standard trim than Dayno's did on Northsides Dyno.

Check out: clubisuzu.proboards29.com/v45index.cgi?board=tripau&action=display&thread=1726

Edit: Fixed Link

[mudgrip4]

Dayno - there is very good experienced advice available on this site. As an old grandad I would rate it as one of the best resources I've come across in 40 years since I began with 4x4s. While people are happy to help to help you get to know your new isuzu, tuning advice offered is not really about turning your truck into a quarter miler - your comment above. Rather, many have walked this path for years and know how to get the best performance from these motors. As active offroaders, we tune these trucks here with set purposes in mind. We use this extra power to improve driveability onroad, to ennable us to push alot bigger tyres on and offroad, and over here to give far better offroad performance in certains conditions e.g. deep water crossings, heavy pea gravel - esp in rivers, and especially for steep climbs, when increases in hp and torque make all the difference.

My last 2.8 did hundreds of offroad tracks on club trips, and especially in southern mountain conditions the extra power is critical. Some climbs are 3-400 meters straight up in rugged terrain - and running out of grunt is not an option when you are faced with reversing that distance down some steep mountain slope. This is why we look for the extra power.

You mention wanting torque increase, and extra low down torque is something we specifically target - alot of rough terrain offroading cannot be rev dependent. You will find the tuning you have done for kws will also have boosted torque significantly. Important for torque is the addition of the bigbore exhaust - you should be noticing the extra pull from low down at 1500rpm now - the turbo spooling in stronger and much sooner.

My last truck improved from a standard 225nm torque to 340nm after tuning and was a very strong little unit. I recall club trips, prior to putting in lsd/diff locker etc, that it accomplished very serious hillclimbs far better than better setup trucks simply because it could hold its power going straight uphill. You should also be seeing some of this torque increase already, and it is no surprise you can out-haul a falcon - I would guess you have much more low rev torque than the falcon 6.

A thought - the simplest and easiest way to monitor any performance experiments is the same test auto mags do when comparing trucks - and that is the standard 80 - 110k passing acceleration test. Get someone to sit with you and stopwatch your truck both directions a couple of times and take the average time. Then in the same temp and wind conditions - don't test in the day time and then again in the cool of the night - test again after e.g. putting in a new filter or trying some other mod. Do this in 4th gear, or if you want to check increases in low down torque try it from 50 - 110ks in 4th - or even 5th. Some of us also have a favourite hill to drive up.

For example, in this test my last swb 2.8 ran 80-110ks in average 6.4 seconds - very quick - with 30.5" tyres. With 32s it ran 7.1. By comparison my present lwb - still being developed - runs about 7.85 seconds. It's an easy benchmark to accurately tell you where your experiments are at. Hope this helps.

Re dynos jimmu - there might be variation in reading from different types of dynos, but should not be if they are correctly calibrated. The hub dyno shop which did mine is a well regarded outfit over here and accurate to within 1kw of manufacturers specs. I wonder though how many shops do take the trouble to keep them correctly calibrated - may well account for varied readings. Another area this kind of inaccuracy shows up is with diesel compression and especially leakdown figures - have seen 10-15% difference in leakdown reports.

Mike

[Dayno]

Well Mike, I tried the 80 - 110km time test, 9 seconds....... Im sure owever because the Rodeo is a LWB Dual Cab StyleSide, It wouldnt weight even close to your SWB car. Currently now, im chasing up where and what kind of Intercooler system would work/fit in the Rodeo. Of course tho after the war my parents gave me over my finacial situation during the 2.5" bigbore upgrade, Im planning to pay off the Ute first, which should be in around about 2 months time. So for now ill use the time to browse and research into an Intercooler.

[geeves]

2 things that need checking that might not show on a dyno.
1 do you have a boost guage if so what boost are you getting
2 check the hose that runs from the pipe between the turbo and intake manifold to the top of the fuel pump for leaks. I had a leak in this and lost a noticable amout of power. I also started showing 5 pound boost instead of 14 as the boost guage is fitted in this line. I tested the turbo before checking this line.

Dual cab ute will be over 2 ton as opossed to mikes swb bighorn that would of weighed in under 1800kg so your figures might not be that bad. It aint ever gong to be a rocket ship unless you go v8. Those acceleration times are ok