4JG2 pistons compared to 4JH1 pistons

[moseswal2]

Hi

I want to use 4JH1 pistons in a 4JG2 motor and I wanted to know if it is posible. Please see attached information from the manuals.

1 - The linner dimensions are exactly the same so lets say they use the same linners.

2 - The piston dimensions overlap but it is posible to select 4JH1 pistons that fits with in the tolerances of 4JG2 pistons, but if the liner bore size is the same would that be nessesary.

3 - The wrist pins are different. I could use 4JH1 connecting rods aswell because the journal sizes are the same.

The reason is, want to convert my 4JG2 to direct injection. I have all the parts, I just need pistons with a combustion chamber.

Your comments and critisism will be appreciated.

Regards

[Roderunner]

Using a piston (s) that has a different weight from standard will throw things out of balance, so I would assume that you would need to use the crankshaft, rods,and pistons from the 4jh1 engine in order to keep the correct (or close to) balance. Machining larger piston pin bores and a combustion chamber into the 4jg1 pistons would best be left to an expert in this field in my opinion. If you are changing over to direct injection for the power gain then it might be more economically viable to replace your turbo with a good aftermarket one, and to add a good intercooler as well. Here is an interactive site that lets you punch in the horsepower figures that you are after, and suggests suitable turbo's that will give you the gain that you want ; http://www.turbobygarrett.com/turbobygarrett/webadviser Here is a good article on how to choose an effective intercooler for a diesel engine: http://www.autospeed.com.au/cms/A_112608/article.html It seems to me that your going to spend a lot of money and time for an increase that would be easier to get using a few aftermarket add ons, still there's nothing quite like the thrill of discovery if you can afford to pursue this crossbreeding of engines!

[geeves]

Someone looked into this a while ago Dont know how they got on. If it was me I would just use a complete 4jj1 or 4jh1 engine but yours might be an exiting alternative. Biggest problems would be ballencing the engine, deck hight, and as mentioned con rod sizes. How would 4jj1 con rods fit on the 4jg2 crank? Might be a better answer than machining the gudgeon holes.

Good luck and take lots of photos

[moseswal2]

Hi

Thank you for replying.

I already have a big front mount intercool and 78mm free fow exhaust and some other things.

I'm after better fuel economy. I wanted to do this combination to have the longer stroke of the 4JG2. 4JH1 piston and connecting rods will fit.

The crank can be balanced acording to the weights of the piston and connecting rods.

The connecting rods can also be shortened if nessesary.

I have posted a few ideas already on this and they were shot down with good reason but this one seems to be holding up.

Regards

[Roderunner]

If you keep the indirect injection 4jg2 engine then you can run it on used cooking oil and/or a diesel/cooking oil mix, now thats good economy if a cheap (or free) supply of cooking oil is available.

[geeves]

direct injection burns this just as well. Look at wbshi007's posts from his 4ja1 powered wizard running biofuel

[Roderunner]

direct injection burns this just as well. Look at wbshi007's posts from his 4ja1 powered wizard running biofuel

The term "biofuel" could mean biodiesel, which is a good fuel in virtually any diesel engine, used cooking oil on the other hand would have to be the worst fuel for a diesel engine around. The direct injection engines just dont have the required compression ratio (and therefore enough heat in the compressed air) to burn u.c.o. properly in my experience, but then there's always someone who manages to do the seemingly impossible (or improbable). I tried a search on wbshi007 s posts and came up with 1 post.

[turnturn]

Try wbski007 (700+ posts)

[Roderunner]

Try wbski007 (700+ posts)

The correct name got me a few hundred posts to read! Thanks turnturn! I didn't read enough posts to see which injection system wbski007 used, but did come across a post where some guy had lost oil pressure after using straight cooking oil for a while.I have found that the used cooking oil dilutes the engines sump oil, making the oil thicken before it's use by date. What usually happens is the cooking oil "polymerises" when exposed to high temps, which means that it turns into a product that looks and behaves like araldite (2 part glue that hardens into a plastic substance). The piston rings end up glued into their lands which increases blowby, which increases engine oil contamination. How soon this happens depends on many factors, like cooking oil composition, water content, combustion temps etc. etc. Having used waste cooking oil as a fuel for around 8 years and over 300,000 kays (and 3 engines) I have found that the engines life will be shortened somewhat. If one is handy with a spanner and can rebuild (or re-ring) an engine for a reasonable price then it's probably worth using, if you don't drive many kays per year then it would be more financially viable to do an hour or 2 of overtime at work, which should pay for your weekly fuel usage.Thats my experience, take it or leave it folks!
)

[geeves]

Will have to apoligise for my deslexic keyboard.
Both engines are 19 to one compression. The injectors though are quite different with the 4jg2 haveing a single quite large nozzle but the 4jb1 haveing 7 smaller holes spread round the side. This I belive is the issue although most cooking oil burners heat the oil to overcome this.
On a similar note ships running bunker oil have to heat the tank to 120C or that stuff sets like tar

[Roderunner]

The half decent compression ratio is a bonus, in fact I decided to supercharge 2 of my previous engines in an attempt to get enough heat into the chamber for a clean burn, the 22-1 ratio of the Toyota 2l was great when running 4-5 pounds of boost at idle, it's a shame that my half hearted engine rebuild contributed to it's early demise! I preheated the veg oil too jeeves, it's probably when one gets greedy and switches over to veg oil before things have warmed up properly that does a lot of the damage, as well as crap oil like that soy, it's better left out for a biodiesel mix. The pintle injectors of the 4jg2 are not likely to block either, but the trade off is that they probably don't atomise the veg oil as well as the multi-hole ones in the 4jh1. There's a lot of competition for the used vegoil nowdays, so I am reluctant to pass on too much info on converting , in fact I don't have any oil coming in right now, and am relying on my small collection in the backyard to fuel my vehicle.

[geeves]

dont worry about passing on info. 30 minutes on google will answer most questions as long as you can recognise the misleading ads and other misinformation there