Isuzu G-series Twin Cam

Been saying for a while i want to put an N/A DOHC in a Gemini, well, things are now falling into place.

First puzzle piece to make its way into the garage was a one-owner 1980 TE Gemini Sedan, stock as a rock, 99000km, no rust and generally perfect condition. Except for the front end [see below].





Story goes the old bird that owned it from new had the bingle, got scared shitless and cancelled the reg and her license. Car was picked up from the auctions for a pricely $325.

So, me and the old man with the help of a few of his mates along the way repaired the panel damage.





The car should be off to get painted by the end of this week - 2pack respray in the standard Atlantis Blue with abit more flake in it.

In the quest for more power, shes going to need more traction. So i got these now too.



Then the DOHC came up on ebay, winning bid of 1525, picking it up this weekend.

AFAIK its a standard G200w EFI with DOHC 5spd, allegedly has extractors and a full exhaust included, full wiring loom and a Haltech E6K running fuel/ign. Also ALLEGEDLY made around the 75rwkw mark as is.







Now, i originally wanted to go quad throttles from a GSXR however seeing as its a COMPLETE package ready to rock, and i dont want to waste time and money if i dont have to, im thinking of using a VN V6 throttle body and POSSIBLY getting a set of cams reground to suit. Well have to see how we go. Aiming for over 80rwkw.

Nick-

good work those figures sound a little bit high but only a few kw's. deffinitley change the throttle body. if you've had a chance to look at it you would of noticed how pathetic it is compared to the rest of the motor.

Do they really lose 25kW (25%) through the transmission?
(St'd EFI G200W is 135HP/101kW).
Might be time to get the GSXR chain as well! (Chuck the carbies - not enough air/fuel delivery.)

Mmm, im using Antus's TX as my yardstick and if he can make 75rwkw with a 2" exhaust, ill be shattered if mine doesnt

Peter, the late model GSXR's actually use quad throttle bodies not carbies. The ones im after are a 46mm butterfly with a 275cc injector from memory. Should be plenty for the old girl.

Nick-

Damn bikes - always changing things. I thought they'd be 36mm or bigger Mikunis etc. But now, a few decades later.....

Also considering that (eg) twin DCOE48s are ideal for a G200W - which is ridiculous for a mere 2 litre - I figured a 1 - 1.5L bike system would be under fueled. But TBIs with enough delivery etc.... Hmmm.

Just keep in mind the "proven" 220+ HP (flywheel) with "merely" twin DCOE45s and manifolds, a 2" exhaust system, L1 cams & a port job, and (unfortunately) pistons to handle above 180HP.

But I recommend EFI on the G200W for various reasons.

Alas I recently sold my Webers & manifolds (HDT-similar jetting to suit G200W) for $1,000.
But the 2:1 "extractors" (from st'd exhaust manifold) was $200; probably about $300 nowadays.
And I think everyone knows of my G200W's 135HP/100kW output (at about 5000 RPM) with 300Nm @ 2k and 360Nm at 3k RPM, and that was a st'd engine except for Webers and exhaust as above. Not bad for simple mods costing under $1,000.

[ PS - I always assumed the above were rear wheel figures. The engine should have increased from st'd 135HP to 150HP with the Webers. But 15HP is too little tx loss. And 135rwHP would suggest flywheel 135kW = 180HP (manual tx) and I doubt the exhaust added 30HP as they were designed for torque. But then again, she did fly....
I recently found the receipt but it said nothing about wheel or flywheel, nor did it give any conversion factor. But I'll re-check to see if it says HP, bHP, PS, etc. It was from Tate's who build/tuned racing engines.]

Thanks Nick for bringing me into this millennium!

Peter.

http://msefi.com/viewtopic.php?t=6627

heres some info on the quads for ya pete

Nick - I hate you. I thought I had left EFI etc for a while....

That's a great link. I have seen it before, but maybe it was this viewing that finally made me see its significance. Wow!

Now my memory is a bit vague (EFI is so last year for me), but....

I think Piazza injectors were about 220cc/m so the GSXR is okay.
But I know people were talking about using Crappadore (VJ?) injectors etc at about 500cc/m.
But was this for 4ZC1t or G200W?
My intention was to go dual injectors (ie, 2x4, not 4+1) - either small+small or small+large. This was in response to others finding that injectors did not have the range required for smooth idle to full power on G200Ws. (Also might be more efficient for mode switching - eg, small for economy/lean, big for race/drag. Oh - just thought, big for petrol, small (underneath the manifold) for nitrous...oooh!)
[IE - does the G-W really suck juice? I know mine would average say 25-27mpg = 10L/100k with twin DCOE45's, but the G-W did things that never made sense to many "experts" - eg, the combination of 48's with L1 cams and huge exhaust (4" and above). The G-Ws are big breathers, yet their economy seems okay?! (FYI - usually exhausts are "the bigger the better" but with discreet peaks - eg, 2", 4", 5", but NOT 3" etc.)]

I'm not knowledgable on bike EFIs, and I'd expect cars to have similar "technology" available. But the bike injectors can deliver high fuel rates (as per your MSefi link), and I would assume "very low" rates also 'cos a bike definitely has stuff-all fuel consumption at idle. (Normal consumption for ~1000cc was ~60mpg or down to 20 if pushed, or 5 to 14 litres/100km.)

Certainly food for thought. I don't like the potential expense though - I'd expect bike injectors are NOT cheap, whereas cars can be dirt cheap.
But it's probably much easier to adapt bike TBs etc. In fact, for once you might have to extend them if "Ramming" is an issue.
And soft mounts, individual & light, beautifully finished TBs. Yeah!

You bastard. Another investigative route.

But then again (you Saviour) - it might be cheaper getting TBs for my GPz900R than replacing the ripped Keihin diaphram/vac rubbers - last quoted at $1,000 for a set (10 years ago. Fk - the whole bike only cost $3k. And they wanted $1k for 4 "discs" of rubber! Farn'L!)

BTW - one time I saw "beautiful" car butterflies was a mate's USA-custom made G200W inlet manifolds (2 x twin port, as for DCOEs). Although this was about 10 years ago, they cost USD$45 each!! The locally made GTR copy manifolds (no butterflies) cost more than that. Yep - the yanks can make beautiful stuff cheaply (that's the advantage of their "user pays" & "3rd world workers" economy! Damned Costello only got us half way there. LOL).

But thanks again. Maybe I should stick to wasting my time at OzGem. This forum has way too much quality! And cruelty - full of temptation and REAL questions!
(Geez, it's nice to be challenged again!)

Cheers, Peter.

PS - another GSXR concern was their hi-impedance (13R (R=Ohm)) injectors.
I concluded that low-impedance was the way to go after someone posted the need to measure injector voltage to vary open times etc (eg: Haltec).
I argued it was much easier to add current limiting to lo-imp injectors (eg - an extra 5c resistor on each injector's driving transistor).
However their info proved wrong - the Haltechs sensed battery voltage, not the injectors'.
But even then, why was there a need to sense battery voltage - just use lo-imps? (Others claim Haltechs are fussy about supply voltage - they don't work well on low voltages. But low impedance injectors have no such issues - excluding ECU design faults; eg - needing above 8V to operate.)
Otherwise each type have their advantage.
But I still preferred low impedance (or dual coil/impedance if available).

Dual injectors... I've never heard of that before, but it's a damn good idea. However, I'd imagine it'd only be a good idea when run as sequential, not as tandem, reason being:

If a 500cc injector has trouble pumping (for example) 40cc/min, then two 250cc injectors pumping 40cc/min, at 20cc/min each, would theoretically be having the same trouble.

Now if they could accurately switch at say, 20% throttle pressure, to open in tandem, you'd still get the smooth idle, but massive flow capacity.

Now I have NFI if that's possible/workable. I'm sure my MSII could be programmed to do it, but whether or not it'd be smooth is another matter altogether. It could be cool to run the second set as methanol though. Petrol as lubricant (or mix a lubricant into the methanol), and methanol as primary fuel OR, as ping suppressor on boost, running in tandem with a knock sensor. YUM.

A few of the car painted...





Goes for road worthy on Monday, thenmid week hopefully reg'd.

And what have we got here?





Dellorto 40mm quad throttles off an Alfa, yet to see if they fit, their on loan from a mate and their pretty wide so im not 100% YET, will hopefully find out in a few days. If i could get rid of the dizzy...

Nick-

No more Mrs = more time to work on the car.

Pissed the quad throttle idea off, too much effort and im pressed for time and cash. This cars being built on a budget. Olds have left for overseas so ive got 7weeks to get this done [*should* be plenty of time, got to keep in mind what CAN go wrong WILL go wrong with me]. Ive got the mighty Yaris to get to work and back in [joy ] or if i get cracked up, ill pull the 200SX out...

Managed to get a VN V6 throttle body, ill have pics of it once my mate mounts it to the plenum for those interested. Need to adapt the TPS off the Haltech onto it, although im pretty sure the Haltech can use the Commo ones, might be easier to do it that way. Any idea if the Commo's use variable or switched tps? Pretty sure variable would be better.

Abit of a "pretty up"



Wrinkle black with polished letters for that "factory" look.

Seems i have not updated in a while...



Engine has been in the car for a week or so now. Had ALOT of problems trying to get it to start, first with no spark, then we had spark and could hear the pump going apeshit but no bang. Turns out the fuel hose under the car i forgot to change was pissing out fuel everywhere and no fuel pressure was getting to the rail

Car is at P.E.T Performance/GTech as we speak, hopefully theyve got it running and on the dyno. Which means i should get her back by wednesday if all goes well.