Toymods Car Club Inc: Tech & Conversions => 2TG/4AG part 2

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Bill Sherwood
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Location:
Brisbane / Gold Coast
Registered:
May 2002

2TG/4AG part 2	Sat, 01 June 2002 23:37

Starting a new thread, the other one takes too long to load up. "The inlet size is only 44.5mm" Ta. I haven't fiddled with one for over ten years ... That makes the curtain area for the valve at 10.27mm lift 14.36²cm, or very much the same as the stock 4AG. "... with an unmodified Squish area. Hence I can't see it causing any N/A Issues." From looking at a lot of different engines, naturally aspirated ones seem to work best with good squish areas and boosted engine don't. Chamber shape is also important, and again that's important as the shape of the 4AG chamber is far smoother generally. "Bill, 2 Valves verses 4 valves is not in contention ! 4 Valves wins hands down. It is 2TG verses 4AGE that is being discussed." That's an inherant part of the difference and can't be waved off. If they both had two valve or both had four valve heads then there'd be little else to compare. "Whilst your 3K and 3SGE comparisons are interesting they are not really relevant to this discussion." I think it is, because it demonstrates quite clearly the difference between an old push-rod two valve engine compared to a good four valve. And that's the basically the main difference between a 2TG and a 4AG. "And yes a 3SGE s#ts on both engines from a great height !* My point exactly, when you bring into the comparison a bored and stroked 2TG. "230hp from your next street engine ?? Would be very curious to see this considering a Formula Atlantic full race engine peaks at 242HP !!" Yep, that's right. The FA boys have a few restrictions that I don't have to follow, as I can make the engine as I please. The computer simulation that I use has so far shown itself to be pretty accurate. Here's the simmed run of the new engine. * Note that I'm not going to be using a 4AG head for that engine, I've found something better that bolts onto a 4AG block. "As for stipulating 1600cc for a 2TG. I hardly think that is a reasonable restriction." Well, it is. As I wrote before if you want to compare the two engines then they have to be the same size. Period. If you want to make it an 1800cc, then let's compare a good 7AG. If you want to make it a 1915cc 2TG (89 x 77) then to be fair you'd have to compare it with a 1998cc 3SGE. And in every case we both know which type of engine will make more HP and torque for its size. "Just because the 4AGE can't be made that big doesn't mean we should discount the point. Oh and as for the 7AGE bottom end being used it is common knowledge that the 7A rods are rather unreliable and the 7A crank does not like to Rev. (Yes I do have 4AGE experience)" The bigget 4AG I've heard of is about 1880cc, using a specially made stroker crank. (83 x 87 I think) That engine revs to 8000rpm no probs apparently. Seems like pretty good revs to me. True enough 7A rods aren't very good, but it's not exactly intended to be a performance engine. There's a couple of threads on those two subjects on the www.club4ag.com forums. The stroker cranks are available from either www.trs-usa.com or Steven Gunter in Jamaica. I haven't followed the 7A rod discussion, but I think there was mention of being able to use a Honda rod instead. "As for "No reason" to pick a 2TG over a 4AGE. How about things like Ease and cost of install depending on Vehicle. Considering that a large percentage of cars on these forums run an A series or T series Block from factory its an important consideration." Fair 'nuf. Though about the only car like that would be the early Celica's, as for all of the other cars you can get a crossmember that has the 4AG bolt-in. It's also not very hard to cut off the mounts of a 4AG crossmember and weld them to a T crossmember. Four cuts and four welds. Either that or make up new mounts for the engine to the rubber buffers, like we did for my Starlet. Took a little planning, but it wasn't that hard in the end. "Bill, In summary I think it would be fair to say this. In stock form the 2 engines are all but equal in performanc Yep, I wrote that before. "Lets be honest, What the 2TG lacks in Head flow or Intake Velocity it compensates for in Cubic Capacity. !! Thats why in either Stock or Race form they are still matched pretty even." No it doesn't. Again, if you want to compare apples with oranges, how about I get a 2.5 litre quad-cam V-6 and race a 1915cc 2TG. Take a wild guess as to which one would win? Okay, to the costs. Again assuming that you own, say, a small port engine. 4AGE head. Porting like my head has cost me about $300. You can use stock valves and springs. My cams cost me $400. Bottom end Don't need forged pistons, the stock ones are fine for 8000rpm. Not sure how much they are stock, but I'd guess about $800 or so. My forged pistons cost me $950 though. Block cleaning and honing, say, $100. Gasket set at most $200 (thats a guess) New belt $40 New bearings $150 Balancing, if needed, maybe $150. (That's what mine cost) New rod bolts - Every engine needs new bolts every time - Guessing about $80 ... ? Extra's that the 4AG will need - Individual runner manifold - Mine cost $20 in materials and maybe $50 in welding and machining. I think you can buy a manifold like that off the self for about $200 odd. Then you have to decide whether to keep EFI or go for Webers or the like. If you have a pair of Weber hanging around that's the only reason you'd want to use them. There's a guy in the US (JSPECPERORMANCE from the club4ag forums) that swears blind that you can use a small port computer with quad throttles. So that might be a very cheap way of keeping EFI on the engine. For throttle bodies, you can either gut the Webers/Mikuni's/Dellorto's (probably the best thing for them) and use them as throttle bodies, or use a 20v set like I have. Paid $250 for mine. Add an alloy flywheel at $450, slotted cam pulleys at ~$200. That totals about $3200, but there would invariably be other little things that would up the cost. It too would put out about 180hp, but have less torque as it's a 1600cc compared to a 1770cc one. You can get (well I did anyway) a 7AF for about $850. I haven't pulled mine apart to look at the rods but I think if you kept the revs down to about 7500rpm it wouldn't be a bother. (just guessing here though) That engine would also make about 180hp due to the lesser revs but more capacity, and also have at least 160ft-lbs of torque if done properly. [Report message to a moderator]

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