More power from a 4JB1-T

[overland47]

Hi guys

I'm writing from the US. I got my 4JB1-T installed into my '82 Isuzu Pup 4x4, and I couldn't be happier with it. It has a lot more power than the C223 I replaced. I wish they would sell these engines here, I want another one now.

Economy is way up too. With the C223 I was getting 22-24 mpg. With the 4JB1-T, I'm getting 28-30 mpg. It pulls like there's no tomorrow, and just all around drivability is excellent.

Now it's time to play. I've gone through all the back posts and made a plan, but I have a few questions.

First I am getting the boost where I want it. I blocked off the waste gate, and the boost will hit 20 psi easily. At freeway speeds, 60 mph (100 km/h), the egt's are down 500 F (260 C), which is a good thing. Before, it was almost always at max boost (10 psi) at freeway speeds. Now it is at about 12 psi at 60 mph on flat ground, which leaves another 7-8 psi avaliable when you put your foot into it.

My boost gauge is tapped into one of the block off plates I made for the egr in the inlet manifold. I have a pyrometer installed. The thermocouple is in the down pipe right where it meets the turbo.

I think I should just leave the waste gate blocked off and use the most boost I can get, but I see alot of you guys are running 12-16 psi. Is there a reason for that? Is turbo life shortened by running higher boost? Will engine life be affected?

Next, I am going to play with the pump. I have tuned several Dodge's with the Cummins 5.9 diesel. They had very similar Bosch VE pumps, so all the methods are the same. I am going to turn up the fuel rate, and make a few adjustments under the diaprhagm. I'm familiar with all this, so that won't be a problem. I'll just turn everything up a little at a time and road test until I get the most power without going over 900 F (480 C) on a long hard pull. That leaves a good safety margin.

My only question is on the pump timing. I want to do that first before I adjust any fuel settings. I have all the tools required to time the pump, and the specs for stock, but I don't know how far I can advance it from stock. It seems most guys are just advancing them to just before they start to knock. Is that right? Probably about 4-5 degrees?

Thanks guys. Searching your site has helped me out a lot with my project.

[mudgrip4]

Had mine advanced and found it gave about 15hp extra. Unsure how many degrees now but it was advanced to point just before it began to knock. Ran in this tuning state for about 100,000ks no problem. Gave an extra 500rpm usable topend revs.

Consider also a 2.5" bigbore exhaust ex turbo. This gave me perhaps another 7-8hp but importantly allowed the torque to kick in much earlier. My truck was pulling hard from 1500rpm after this addition, rather than 2000-2200 before. And a good aftermarket filter ( I used a K&N ) helped the tuned up motor breathe very well.

Mike

[overland47]

I should have added that I have 2.5" mandrel bent exhaust from the turbo back, with no muffler.

I have a custom cold air intake that is 3" (with a high flow, but good, filter) to the original crossover above the valve cover that connects to the turbo.

So it breathes well ;D ;D

Also, this is an intercooled engine.

Thanks, keep the tips coming. I am curious as to why nobody is running higher boost, as mine will do 20 psi easily, with the stock turbo.

[roga]

I have been running 20 to 22 psi boost for about 8 months both around town and offroad in local 4wd club and have had no probs so far. Is intercooled with a k&n filter and a 3'' exhaust from turbo back
Performs well and can surprise quite a few of the smaller cars around town.

Your pup is what they call an early model Holden rodeo over here

[overland47]

Thanks roga.

What did you do to get that kind of boost? Did you block off the waste gate completly?

I've been thinking it over tonight, and I don't think there would be any ill effects to the turbo. Thats what they are designed to do after all. My concern now is the head gasket and engine internals. If you've had your's like that for 8 months now, than any problems would have came up by now.

I tweaked the diaphragm a bit a bit tonight with huge results. This is essentially the "top end" fueling, after the engine has started to make boost. I will be turning it up a little more though, as it's not smoking at all and egt's are down pretty low under full power at high rpm's, so it has a ways to go yet. It pulls a LOT harder on the top end now. Boost is up to almost 25 psi also.

I think I am going to set the waste gate to 25 psi for now to be safe as I tweak the pump until I get more info on what a good max boost for these engines is.

I am going to do a full write up when I am done with lots of pics and details, as the info is out there now, but it seems to be pretty scattered and it is a common question people have. It's a slow process though, tweak a bit and test drive, and then tweak a bit more kind of thing......

[geeves]

If the engine is in good condition its the turbo that will suffer first so it would be worth checking the specs with IHI. The only reason Im running 14psi is that is what the guage read when fitted. I have a restrictor in the guage plumbing that gives a steady needle at idle but if I remove the restrictor it give 17psi. I dont know if mine was tweaked before I got it or I have a fault that Im in no hurry to fix

[roga]

What did you do to get that kind of boost? Did you block off the waste gate completely?


No I use a boost tap in the line between the turbo and the wastegate
it bleeds off the excess so that the wastegate operates when you want it to.
I think that the main restriction now in mine is the intercooler so I am looking to find a way of putting a larger flow core into the original tanks.

[flatlander07]

Tell me more about the fuel economy. I'm on a max mpg quest with the same exact motor. Saw some great stuff on a site by you. Last entry was gonna drive it like grandpa mode and report back. Never could find the findings. Is it FWD? Is it lifted? What size rubber? Rear end ratio? Do you get that 30ish wailing on it?? Do you have a Grandpa mode mpg figgured out?

Thanks in advance for any light you could shed on this stuff.

[geeves]

How does your Dodge compare in size to a Trooper? On my bighorn which is a 89 trooper x japan with this engine on the open road 33 MPG (english not american) is achieveable. This is reasonably easy country 31 inch tyres 4.3 dif and trying hard to stick to the 60MPH speed limit

[flatlander07]

My big Dodge gets 20 mpg max. American. 6BTA Cummins.

The Dakota I'm trying to build is about 4,000# with 30 inch rubber and 3.55 gears. The standard drag coefficient is .47, and I hope to get it down to .30 at least.

I'm going for 48 to 53 mpg American.

It appears that you get about 2/3 of the Cd reduction in fuel economy.

[flatlander07]

I always struggle with the Imperial gallon stuff. How does the 33
mpg convert to American??

Oh yeah, size wise, the Dakota is 66 in. tall in stock 4WD. Looks like I can only lower it 4 inches max.

[geeves]

from memory the us gallon is smaller than the english one but not sure how much. Google should be able to find a converter. If not convert from liters/100km to us mpg The answer on this is 8.3l/100km
Just had a look at a few specs on the dakota similar weight to the trooper but more streamlined and lower roof. You should better my figures but not by the amount your aiming at unless you also drive in a very conservitave manner. Anouther way to get the hight down is a hot rod style top chop

[flatlander07]

Yes, it's all speculation. Google Banks sidewinder project. They got a Dakota down to a claimed .17 drag coefficient.

Committed to a Dakota, so I guess I'm doing it. Be interesting to model the engine in there and see if it fits.

[JustinW]

1 UK gallon = 1.2 US Gallon (actual conversion is 1.20095 but 1.2 is near enough)

[geeves]

so 33mpg Uk = 28mpg US roughly

[marckb]

Hi guys ,

Has anyone considered water/methanol injection for more horsepower and cooler engine / lower egt , seems to give up to 70hp on some engines . Summitracing.com has different types of this system available .

[geeves]

Never ran into methanol for diesel before sounds interesting except for this quote from there site
The combustion of water provides more power on the power stroke
only way I know to combust water is to electrolys it first but isnt that realy burning hydrogen

[overland47]

Sorry guys..been a few days since I've checked here.

I got up to 31 mpg US in "grandpa mode". I don't think it makes much difference if it's driven hard or light.

Since I've turned up the pump, I have run 2 tanks of fuel through it. Not driving for economy, just driving....sometimes HARD....and it is down to 27 & 28, respectivly. Something still doesn't feel right; it feels like it is dragging somewhere more than it should, but I can't find anything.

It is 4wd, 29" mud tires with pretty agressive tread, 4.10 rear end, 3" body lift. I added another 20 psi. to the tires...up to 55 psi, so we'll see what that does.



I still have some tuning to do to the pump, and then I'll have a full report. I decided to wait to finish until I can do it on a dyno, right now I'm waiting for some shop time. If I wait until it's open with no appointments, I can use it cheap

[geeves]

4.1 diff is quite a high ratio and the 4jb1 is a high reving engine that even with big exhaust and high flow intake doesnt realy like being below 2000rpm which could explain things. You should be aiming to tweak your ratios so you have 2000 to 3000 rpm at your open road speed limit. Im running a 4.3 dif and changing from 31 to 32 inch tyres made a huge difference to pick up but ecconomy didnt change and once up to 100kph you hardly notice the difference With the 31s 100kph was 2400 with 32s its 2200 This is adjusted speed not speedo reading.

[powertruck]

Hey with your egt's i run mine pre turbine in the manifold. ive found if you run it on the downpipe you can see as much as 150 degree drop so its not as accurate. My egt's around town sit around 4- 500 degrees F if im on the open road in they creep up to 700f under load up a hill i can get them up to 1000f depending on what gear i am in.
With my probe in the back of the exhaust my measurements were way off. Just remember the IHI turbine wheels are designed to run at a constant 900 degrees c so i would take your measurement pre turbnine before you start playing around with the fueling just to be more accurate

Just a thought