Advice.... --(Jaysin)

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

i have a mildly worked 1.8 ltr gem. (cam, extractors, exhaust), yet i know the engine is not in the best condition. I am either thinking of getting it rebuilt and shaved, polished etc or simply spending the money for a faster engine. Which would be the best and cheapest way to get a realiable more powerful engine?

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

rebuild it as it will out power a g200 and can run the 2l pistons and has a longer stroke than the G200. Give it a mild port job and shell fly

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Dpends on how much more power you want. You wont get much more from simply porting the head an shaving for compression. It might be noticable with the 'seat-of-the-pants-ometer', twin carbs would make a noticable improvement in power, but it still wont be a big difference. Maybe a 10% power increase.

You have done the most effective mods, except for a carb swap, you haven't mentioned anything. The cheapest way would be to shave a couple of mm off the head, get a verneir timing set to advance the cam back to its specified timing, and buy a DGV weber and adaptor plate, and port the buggery out of the manifold.

This still does not address the engine problems that you are having, but either doing the above or going for the ultimate power increase like bolting on a turbo will still requre a decent bottom end. With heaps of blow by from worn/damaged rings and pistons, you are pushing shit up hill. You might find the biggest gain is to be had by re-ringing the engine, posibly with new pistons, as this will seal in your cylinder pressure. Theres not much point in having more compression if it just leaks past the rings.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

I think somebody is getting a little one-track in his replies.... there are other options than turbocharging.... like.... er.... um.... fitting a CA18DET.... mmmm...

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

bolting on a few manifolds and installing a few oil lines is going to be a shit load easier (and cheeper) than trying to fit another engine in

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Or fitting a 4AGZE (??) supercharger, IMHO a damn site more useable than some fuqqin hair drier Wink

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

better the devil you no !!!!!

or trottle in a bottle : )

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

But superchargers dont give you the whoosh sound, just that silly belt noise.

And depends what you mean by usable. If you mean loosing traction in 4th gear from simply flooring the accelerator pedal, then no, a turbo is not that usable. But that was in the wet.

In the dry, I'd rather have full boost at 3000rpm than wait untill the engine redlines.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Speaking of CA18DET's, a mate is selling one, he wants $600, I think I could get it for about 500. Its in a bluebird, with 5 speed, standard computer, apparantly has a VL turbo pump. No diff centre, and might have knackered big end bearing.

It might be a futre project to add to the list. It'll probably go in my circuit racer, as I'm buliding another gemy as a street sleeper. TD, Plain satin paint job, standard height soft suspension, small exhaust tailpipe, reasonably quiet, factory hubcaps, tissue box on the parcel shelf, lawn bowls sticker on the c pillar window, and 300hp to smoke the skinny 205's with.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Hey ben what you on about?

a supercharger gives instant boost

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Yes, superchargers can be geared to give boost at idle if you want, but they wont reach their maximum boost output untill your engine is revving at its maximum speed, as a superchargers boost is a function of engine speed.

A turbochargers boost on the other hand, is a funtion of exhaust gas, which is not solely dependant on engine speed. It is actually more dependant on engine load, or in other words, how far you are pushing down on the accelerator pedal.

Thus, you can have a turbo that spools up and produces maximum boost (say 7psi) at around 1500rpm, all the way to 7000rpm, when you floor the accelerator, whereas a supercharger that outputs 1psi of boost at idle (say 1000rpm), and if limited to the same boost as the turbo, wont put out maximum boost untill 7000rpm, regardless of the engine load, which is really how much the driver wants extra torque at any one time. You want acceleration, you put your foot down.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Ahhhh thanks ben
i never been told that before
see all i was told about blowers was that there is no lag and the boost is just there

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

they beat the hell out of N/A engines, but unfortunately they take a shit load of power out of the engine to run. Just look at drag cars etc, the belt is massive and they still snap. A turbo on the other hand is running on exhaust gasses.. you will have this on any engine as all they effectively are is a massive air pump - so if you make use of it then its pretty much as close to 'free' power as you can get.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Yeah, the roots type and others as used on top fuelers have a very high parasitic power loss, but there are the centrifugal sort which is basically a belt driven turbo compressor (there is also a gearbox associated). These dont sap as much power as the other sorts, but they still suffer from the boost/rpm rule instead of boost/mass of exhasut gas that a turbo follows.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

"Centrifugal sort"...you mean a roots blower?

Paul
Never late in a 308