BALANCING MODIFICATIONS, SNORKEL, EXHAUST ETC.

[gomulletgo]

Hi guys,

I'm planning to try and mod for a bit more power soon enough (89 bighorn 4JB1 2.8ITD). I've got my oil catch can on, boost and EGT guage in, service done, will do cambelt soon. Once exhaust and snorkel are done I will be winding up fuel and boost at the very least and possibly swapping a subaru turbo in. I want more power lower in the rev range aswell as more power up high in the rev range as nothing really happens until 2300rpm.

I'm thinking I will go with a steel 3inch dia snorkel, I prefer the look of plastic snorkels, but no one can tell me how restrictive they are compared to a 3inch steel one.

I want to know what size exhaust people think I should go for, keeping in mind that I want low restriction and will be modifying the engine for more power. I will probably make the exhaust myself, so all I need is to know the size 2.5? 2.75? 3inch?

Also does anyone have any idea where to get cheap exhaust pipe, bends or donuts and flanges?

I think that's all for now, obviously I will have to do the 3.1 filter swap and block off the overboost protection.

Thanks in advance

[gomulletgo]

Also I've been reading a bit about boost controllers, If I put an in cab boost controller in and wanted to run say 13psi most the time and then wind it up to say 18psi for overtaking etc. Would the fuel pump adjust to the different volume of air going through? Or is it static? Would I be best to have the fuel wound up to cope with 18psi and then just run it inefficient all the time? Or have the fuel wound to cope with 13psi and then run it lean when it's running 18psi? Cheers, I hope that makes sense

[geeves]

I would leave boost set high The fuel pump has a compensator so will adjust fuel to the boost. If you dont use high throttle settings you dont get full boost. On the flat at 100kph I only have 5 pound but put the foot down and its straight to 13 or so.

[MattMu]

Mullet do you understand how a diesel works? Your comment about running inefficient suggests you have no idea.

Running a diesel inefficient as described is called over fuelling, there is no such thing as lean or rich in a diesel. If you run lean...well thats just less throttle, running a diesel rich (overfuelling) is terminal!

You will at least, melt the pistons, melt the turbo, melt the exhaust valves....so basically you will destroy the engine.

The engine requires just enough fuel to operate at the given load and its not a guess. The tuning you are contemplating requires a few hours on the dyno getting the max boost matched to max fuel and measuring the result with EGT.

The boost figures you are talking about are pointless too, simply adding massive load on the turbo for little gain. So basically you will kill the turbo for nothing. The 2.8 MUs have a pressure valve in the manifold that prevent you going much over 10psi anyway. Not sure if the 2.8Bighorns do also.

The fuel pump will restrict you getting full fuel but it will not adjust between two boost settings. It is simply a restriction on the "throttle" plate until a predetermined boost is reached, so you could run the engine at 13 psi (still way too high) and have the fuel restricted at that point (gutless) so that when the boost reaches 18 (rediculousy high and pointless) you get the max fuel tuned for that psi.

Againthis is all semantics because your engine would be dead before you got all this to happen.
Do you want this engine to last a week or two or do you want it to be reliable and still pull like a little truck.
If you want the latter, you can fit the exhaust, fit a standard snorkle(more than adequate and good for cooler intake) and then fit a boost controller set at about 12-14 MAX. You will then need to get it on a dyno for the load screw adjustment for a reliable fueling ratio and while its there the diesel guys can also check your pump timing is spot on too(can be out from new).
Goodluck and enjoy!

Matt.

[geeves]

Overboost on the bighorn is preset at about 15psi

[lewis]

Ive fitted a k&n apollo filter, removed the stock muffler, blanked overboost valve and am running 1/4 turn up on the pump and 15 psi using a bleed valve. Also venting the crankcase breather. Mate is making me a 4" stainless steel snorkel in the next few weeks (no 3" offcuts available). Only get 15psi foot flat at above 2700rpm or so which is not very often. Tend to see 5-11 on most open road driving. My truck is not intercooled
Done about 3000km and it goes great, goes better on 33s now than it did on standards. Never gone above 600degrees exhaust temp in the manifold. Long hills it likes to hold just below 600 if u try and go hard so I tend to back off and drop a gear - would like to fit larger exhaust so I dont have to do this, would go for 3" back from the flexy and 2.5" for the first section so I can still get at the oil filter (from what i read). However that costs a lot hence not bothering yet. My engines done 340km no rebuild and I dont see it dying any time soon. 2000km of that 3000km was a single road trip and didnt burn a drop of oil either However im not a diesel mechanic so time will tell!

[haven]

Ive fitted a k&n apollo filter, removed the stock muffler, blanked overboost valve and am running 1/4 turn up on the pump and 15 psi using a bleed valve. Also venting the crankcase breather. Mate is making me a 4" stainless steel snorkel in the next few weeks (no 3" offcuts available). Only get 15psi foot flat at above 2700rpm or so which is not very often. Tend to see 5-11 on most open road driving. My truck is not intercooled
Done about 3000km and it goes great, goes better on 33s now than it did on standards. Never gone above 600degrees exhaust temp in the manifold. Long hills it likes to hold just below 600 if u try and go hard so I tend to back off and drop a gear - would like to fit larger exhaust so I dont have to do this, would go for 3" back from the flexy and 2.5" for the first section so I can still get at the oil filter (from what i read). However that costs a lot hence not bothering yet. My engines done 340km no rebuild and I dont see it dying any time soon. 2000km of that 3000km was a single road trip and didnt burn a drop of oil either However im not a diesel mechanic so time will tell!lewis
Isuzu Junior

a few things on this. running such boosts without a tune and more so an intercooler is crazy, you are severly increasing the load on many engine components and risking catastrophic failure, juts because you can do something and it works for a short period of time or juts because some wanky mod can be done to a petrol car and it takes it doesnt mean it works will diesels, they are very precisionly tuned machines, if it was as simple as winding up the boost as you saw fit the dealerships and manufacturers who employ engineers for hundred of thousands of dollers would have gone , oh shit lets give the mu a few extra kw's....


in the exhaust department, your exhaust is ONLY as good as the smallest restirction, having 2.5 inch dump pipe and a 3 inch dump pipe back is a complete waste of time. having 2.5 inch dump pipe means the air restriction at that point is set, no matter if you run a ten inch exhaust the rest of the way you still have a 2.5 inch exhaust, pick a size and make it that size the whole way.the fact that your motor has done 340,000 hints that its getting old, on top of which your tweaking the settings and trying to drag more power out of it. for all the effort you could probly replace the rings and gasket and get more power from that purely of good compression than anythign else.

[lewis]

Things are built with huge safety factors at the factory so I think there is room for safe power increases, as other members on this forum have demonstrated.

The truck rarely sees foot to the floor and above 11psi boost and pretty much never sees above 3k revs so all this massive load on engine components you speak of is not for extended periods of time

The truck itself is worth bugger all so im quite happy to keep it running as it is and if it blows up soon hey ill learn my lesson and pull all the bits ive added and onto hte next truck.

I cant imagine an intercooler dropping the intake temperature by that much, especially when its mounted above the engine, and probably dosent do much (maybe even becomes a heater) when you are going slow offroad and a fan can only do so much.

Surely length has some factor in exhausts - would a 2m 2" exhaust be worse than a 4m 2.5" system?

You can tell me my mods are wanky and of course i dont know more than japanese car engineers but Ive probably spent less than most people do and am happy with the results.

Just cause mods are cheap does not mean they are poor, some people give away $200 to get someone to change their oil and filter...
There are always people out there willing to throw away money because they dont know any better (no I am not saying I am a diesel expert, just stating the case)

As I am not a mechanic changing the rings and gaskets would mean my car is off the road for quite some time as it would be a learn as I go approach. I only have one car so dont want it off the road for ages unless it needs to be. These parts are probably not cheap either

My 2003 CR250 is meant to have 'by the book' piston changes every 20 hours or something. Ive done an estimated 200hours (not racing however) and it starts and runs great with all the power in the world. Sure it might blow next ride but thats life and i am sure not going to start changing it every 20hours if it does.

Each to their own eh...

[geeves]

There is nothing unusual in your approach to mods. Im of the opinion that exhausts get changed when they need to be changed as you need to spend the money then anyway. The snorkel will increase power when you fit it but more importantly allow power at lower revs. Intercooler does make a difference on road. I did some measurements on mine and was seeing 45 after the turbo and 25 after the intercooler measured by a sensor tapped to the outside of the metal pipe. I didnt try at low speeds. Your EGT says you are not overdoing things although that is right at the limit. A bigger exhaust will lower this but if your current exhaust is good why spend 800 + right now The snorkel will lower this as well.
As for tuning the only things that can be done are pump timing and tapets. If your tappets are right and the timing doesnt shift by itself so is most likely right then your fairly sweet. Setting the fuel rates should be done on a flow bench but this means taking the pump off at high cost. A diesel specialist reset mine after doing the external seals and it ran better than new afterwards. Dont know how much the fuel level was changed but it lit the 31 inch tyres by accident leaving his driveway. (I took off like I had to before oops)

[lewis]

Yeah i didnt think there was much else 'tuning' that could really be done as unlike a petrol engine we dont need to get on a dyno to test if its running rich or lean etc

I have turned the fuel down to 1/8th of a turn so that im not near 600 degrees so much as it was annoying to have to back off on hills last weekend with the truck loaded up as I dont want to hold it at 600 for the lenght of the hill. Definitely seems like a bit of a drop in power before 2300rpm with the fuel decrease but still not going to rush into an exhaust as think i need to spend elsewhere - looks like im going to need a new power steering box as its leaking pretty badly, i guess extra stress from the 33"s

Unlike haven I still think length is a factor in exhausts - id rather have it larger than stock in one section than stock all the way

[geeves]

I did mine in 3 bits. First the tail pipe rotted out so that became 2.5 inch from in front of the diff then the center pipe became crushed so it got 2.5 inch as far as the expansion joint. One day this will give up and the front/dump pipe will be done. Each piece gave a noticeable improvement over what was there before. Even 2.5 inch tail pipe and two inch as far as the back seat was better than 2 inch all the way.
Not the best way to do it but it does work and the bank manager prefers that way.