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Location:
Brisbane
Registered:
October 2002
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Mon, 18 August 2003 08:44
 
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that really depends on the limiting factor of the motor. if it has a long stroke or a very undersquare bore/stroke ratio, then it wasn't really designed to rev that much.
two things you have to think about. the engines ability to breathe at higher revs, and the engines ability to stay ogether at high revs 
would 11:1 or 12:1 not be a little too high for even 98 octane?
studs are good because they are usually made to high standards, and you get more reliable clamping force, and saves wear on block threads etc. they are always good, but not always necessary. don't rods have studs anyway?
i would guees that mains would be fine, but new rod bolts and head studs might be a good idea if you are really looking to rev the thing.
head gasket? depends on the compression and if you have pinging or not. detonation is the real head gasket killer imo. gaskets like ACL Monotorque are pretty good quality, but if you are really worried, get a copper gasket.
power? no idea. what rev range are you after?
Cya, Stewart
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Location:
1st street on the right
Registered:
November 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Mon, 18 August 2003 11:01
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Stud the head, it should also be better for the head in some way that I read once be temporarily escapes me. Also from memory Ridgecrest don't make a copper gasket for 18rg (if this is wrong or someone else does let me know).
11/12:1 is high for 98Ron, where were you getting pistons like this as I'm also trying to source some (though only around 9.5:1) JP's in Adelaide haven't made 18rg pistons previously and require specs which I'm also trying to get (anyone, anyone). A metgal gasket would let you "play" with comp ratios if the pistons you want aren't available.
The rods should be studded, studding the crank isn't a bad idea for higher revs.
Bore stroke for 18rg is 88.5 x 80 (though another source says 89x80, confirmation) and so is over square, good for revving.
Good cams, the right head (88253 has larger valves) balanced and well built
shoud be strong enough and have adequate power for N/a motor.
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Location:
1st street on the right
Registered:
November 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Mon, 18 August 2003 11:03
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Stud the head, it should also be better for the head in some way that I read once be temporarily escapes me. Also from memory Ridgecrest don't make a copper gasket for 18rg (if this is wrong or someone else does let me know).
11/12:1 is high for 98Ron, where were you getting pistons like this as I'm also trying to source some (though only around 9.5:1) JP's in Adelaide haven't made 18rg pistons previously and require specs which I'm also trying to get (anyone, anyone). A metgal gasket would let you "play" with comp ratios if the pistons you want aren't available.
The rods should be studded, studding the crank isn't a bad idea for higher revs.
Bore stroke for 18rg is 88.5 x 80 (though another source says 89x80, confirmation) and so is over square, good for revving.
Good cams, the right head (88253 has larger valves) balanced and well built
shoud be strong enough and have adequate power for N/a motor.
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Location:
Perth
Registered:
May 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Mon, 18 August 2003 16:33
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Agree with the other members, that if you can afford to stud the head, then do so. The mains aren't as important, but would also be a good idea. I have read that you can have the rods reamed and use Chev ARP rod bolts, only coz finding hi-po rod bolts for the RG is like finding hen's teeth.
11:1 or 12:1 is a bit high for 98 octane. Stick with 11:1 or 11.5:1 max and use optimax (102 RON?). Preventing detonation will be the key, but provided you properly set the squish gap you shouldn't have too many problems. From what I have read and heard the hemi chamber seems to be less susceptable to detonation in comparison to closed chamber heads such as that on the 4.1 falcon and numerous other motors.
18RGs are built to rev, the limiting factor being the con-rod strength. As you probably already know, con-rods generally break in tension (caused by high revs) as opposed to breaking in compression. (Assuming good oil supply, no detonation, no NOS ) A safe limit is 7200RPM for cast rods and crank, but I have read/heard of people who have gone past this with out problems.
As Stewart has said, provided you keep away from detonation, you shouldnt have any problems with the standard gasket.
clubagreenie, I am sure that ridgecrest can custom make any gasket, but don't quote me on that.
I am also very interested if you do find a supplier for high comp pistons.
Definetly balance the motor !!! Don't take too much off the flywheel (plenty of threads on this).
If you can get hold of Desktop Dyno 2000, it is meant to be able to predict the output power and torque to with-in 10% of acutal figures given reasonable input values. It is OK for NA, but not so good for turbo applications. Using the program you can also develop the best cam profile for your application, then all you need to do is re-grind a set of old cams to those specs (or as close to as possible). A lot cheaper than sourcing TRD cams
Bugger, thats a long post.
Time to shut up now 
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Location:
Brisbane
Registered:
October 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Tue, 19 August 2003 00:58
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well i was told that JP engineering in adelaide can do 11.5:1 comp for like $800 odd, my dad owns a speed shop in townsville and he's the one who owns the engine, so he'd do all the work labour free 
i was thinking of having a redline of MAX 8000 but 7200 or 7500 useable.
i was hoping for maybe about 220+hp that'd make a nice little sleeper.
i wasn't sure about the 12:1 comp but 11:1 would be ok since honda's run 11:1 in the S2000 and others, {i know they're efi ect ect}
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Location:
Adelaide
Registered:
June 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Tue, 19 August 2003 05:08
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Clubagreenie,
Yes, JPs have done 18rg pistons before. Every time I ask them they can't find them in their books, but trust me, they have, I've seen them. They were for a bunch in Tassie, but were for 18rgu head of 1982 vintage. The people who ordered them can't remember ordering them, it was for a client of theirs a few years ago now.
I can give you the specs on them if you want. I have that at home.
They can also do a 91mm bore with a stock shape dome, to what ever dome height you want.
Yes, 11:1 is very high for 98 octane fuel, it will ping its head off. I have heared of a guy who went through many, many head gaskets with 11.5:1 in an 18rg and eventually had to get
it decompressed to 10.5:1, now it's OK.
If you want knockoff original 9.7:1 pistons, I could do a little running around and I reckon they could do that for you as I have all the critical measurements of those pistons at home.
Philmelvin.
I made the post about the price and it was $660 GST inc. with cast iron rings and I think with gudgeons(these rings will need to be swapped for chrome ones, which are available from hastings, I have the part numbers for these rings if your interested.
EVERYONE PLEASE NOTE: these pistons are CAST, if you're after forgies these are not for you.
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Location:
Adelaide
Registered:
June 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Tue, 19 August 2003 05:16
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If you go for high compression you'll most likely want some pretty serious cams as this would reduce your chances of serious detonation problems with high compression pistons and low duration cams.
Toyota ran 11.5:1 pistons in their 18rgs and also 10.5:1, but they were getting max power about 7500 - 9000 RPM, which is where the cams appropriate for these types of compression figures would be putting you.
Unless you are willing to hugely raise you're redline, I wouldn't go too high for your compression or low cam overlap will cause problems.
Summary:]
high comp + big cam = great power but @ high revs.
High revs = less longevity of engine (it'll die sooner)
high comp + small cam = good power but dead pistons (detonation)and headgaskets.
If there is anything else you'd like to ask on this topic I would be happy to try to answer your questions.
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Location:
Brisbane
Registered:
October 2002
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Location:
Perth
Registered:
May 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Wed, 20 August 2003 05:59
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The pistons will have to be flycut, even using standard cams. You could still have pistons made to give a final comp of 11:1 after being flycut.
Provided you select reasonable cams, it is unlikely your power curve will be like you have shown. From what I have seen that sort of curve is typical of a turbo engine, generally with a MASSIVE turbo that doesn't come on boost till 1000000000rpm (slight exageration there). NA engines tend to have a less steep curve.
For an everyday driver, you are better off staying at say 10:1 to 11:1 and selecting the cams for a strong mid-range torque curve as opposed to aiming for peak HP. It will make the car a lot nicer to drive. It would look silly doing a 5000rpm launch just to beat a stock lancer across the lights because your engine makes little torque down low 
Depends on where you are wanting the power to whether 40's will be big enough. EFI is definetly a nice option, even just for the 'tuneablility' it offers.
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Location:
nth ringwood, Victoria
Registered:
August 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Wed, 20 August 2003 07:14
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dream on guys no way will you get 200 hp ,in group C days with 12to 1 comp and 320 duration cam s and 450 thou lift plus mechanical injection and extractors and trd valves and springs and dynoed ,engine dyno here 185 tops and that was for 1000 klms then pull down and rebuild red line was 8500 power was btw 5000 to 8000 rpm ,so it would be good going up to the shop with avgas in your tank hey my 2 cents worth ,for the record my 3sge altezza engine also 2 liter has 535 thou lift cams and 300 duration and im running 11.9 to 1 on BP ultimate and its making 242 at 7600 at 8000 it has lost 5hp and my power is 4500 to 8000 and thats with TRD parts as well
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Location:
sydney
Registered:
April 2003
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Location:
Sydney
Registered:
January 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Thu, 21 August 2003 03:37
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Just a note, Optimax is on average 98RON, BP Ultimate on average is 98 RON, Caltex Vortex(yuk..) is 96RON on average.
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Location:
Brisbane
Registered:
October 2002
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Location:
Brisbane
Registered:
May 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Thu, 21 August 2003 08:58
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If you want a relatively quick car without spending a small fortune, you'd be silly not to go the turbo route!
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Location:
adelaide
Registered:
May 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Thu, 21 August 2003 13:37
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yes i agree with norbie, this is what im beginning to realise.
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Location:
South Australia
Registered:
August 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Thu, 21 August 2003 14:16
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Cliff Hansen from Australia wrote: I am the owner of a fully restored RA28 Celica 3/1977, had since new. Turbocharged 18RG bored/stroked 2400,21psi to 6600rpm. On the outside. it's all Celica, on the inside, 280hp at the wheels. Intercooled,17x8" wheels, 81/4" diff,4 piston calipers 12"rotors front. Single piston 10" rotors rear. i sent an e-mail and photo before, so i hope you get all of this. I'm also a member of the Celica Car of Queensland / tccq groups yahoo P.S. The car is not for sale.
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Location:
Brisbane
Registered:
May 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Thu, 21 August 2003 22:56
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Cliff's car is pretty impressive... I'm not sure how this is relevant to the discussion though?
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Location:
South Australia
Registered:
August 2003
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Re: high compression VS rev-ability of Hi-Po 18RG
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Fri, 22 August 2003 03:15
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Im just saying that its possible to get them over 200hp
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Location:
Brisbane
Registered:
May 2002
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Re: high compression VS rev-ability of Hi-Po 18RG
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Fri, 22 August 2003 03:43
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Of course it's possible with a big mofo turbo slapped on the side, but the discussion was about naturally aspirated 18R-G's.
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