Hello, my name is Tony and I am new to this thread and would like something clarifying if possible. I actually drive an MG Midget (1973) fitted with a 4A-GE engine from a Corolla Liftback, this gives the car terrific performance with excellent fuel economy. However I had the car on a rolling road and found out that I only have 78 bhp at the wheels, how do I find out how much horsepower the engine should actually produce ?. I would hope to get a few more bhp at the wheels.
it depends on the 4AGE you have, do you know what car it came from? (i assume its not the stock engine). from the power output it sounds like it could be a smallport non tvis 4AGE.
also, is the engine in good running order? plugs, wires, cap, rotor all in good shape? intake and exhaust system in good order?
The engine now grew to 1275 cc using the development seen on the Mini Cooper S. Output was 65 hp (48 kW) at 6000 rpm and 72 ft·lbf (98 Nm) at 3000 rpm. However, this was a de-tuned version of the engine that was given to the Cooper S. The Midget retained the standard 12G940 cylinder head casting that was common to other BMC 1300 cars, whereas the Cooper S had a special head with an extra two bolts to fasten it to the cylinder block. The hood was now permanently attached to the car. There were minor changes to the body in 1969 with the sills painted black and a revised black grille. "Rostyle" wheels were standardised but wire spoked ones remained an option. The square shaped rear wheel arches became rounded in January 1972. Also in this year, a Triumph steering rack was fitted, giving a gearing that was somewhat lower than earlier Midgets. A second exhaust silencer was also added in 1972.
22,415 were made between 1966 and the 1969 face lift and a further 77,831 up to 1974.
so the 4AGE is quite a kick in the pants over stock power, since those are crank figures not wheel figures. 80bhp is probably 30-40 more than what it would have made with the stock engine!
the stock 4AG on the corolla liftback, in good running order should be 90-100~ at the wheels.
How you get 78 on a little MG, is just mind boggling. Something's not right...
well its rwd, so you need to figure higher driveline losses and the dyno calibration can play a huge roll in it.
Quote:
Power output for the 4-valve version varied widely, from 112 hp (84 kW) at 6600 rpm to 138 hp (103 kW) at 7200 rpm. Again, torque was closer, varying from 97 ft·lbf (131 N·m) at 4800 rpm to 110 ft·lbf (149 N·m) at 4800 rpm.
it also really depends what 4A-GE he has, an early smallport didnt put out that much power over a later model 4A-FE!
Thanks for your replies, much appreciated.
The engine is a TVIS type, I think it came from an 87 Corolla Liftback. I was led to believe that the hp was 120+, although after looking through varoius 4age web pages it seems that there was a 88bhp engine produced so I am wondering if I have one of those. Was there an AE85 produced as this seems to ring a bell ?
Thanks
Tony
well its rwd, so you need to figure higher driveline losses and the dyno calibration can play a huge roll in it.
it also really depends what 4A-GE he has, an early smallport didnt put out that much power over a later model 4A-FE!
I'm aware its RWD, in fact when I said 90-100hp at the wheels, thats a figure from the AE86s. Think about it, a MG Midget is much lighter man.
And theres no such thing as an "early smallport", there is only ONE smallport 16V 4AGE.
Early bigport 16V= Stock on the AE86s, 112HP-130HP (Depending on region)
Later bigport 16V=Came on last gen AE86 (1987) and early AE92s (1988-1990). 112HP-130HP (Depending on region)
The smallport 16V (aka redtop)=Came from the 1991 AE92s. No TVIS, 130HP-140HP depending on region.
So as you can see, I'm already assuming if he has a 4AG, its the earlist weakest one. And even that doesn't make much sense from his numbers. Also any 4AG will put out more than the 4AFE.
Thanks for your replies, much appreciated.
The engine is a TVIS type, I think it came from an 87 Corolla Liftback. I was led to believe that the hp was 120+, although after looking through varoius 4age web pages it seems that there was a 88bhp engine produced so I am wondering if I have one of those. Was there an AE85 produced as this seems to ring a bell ?
Thanks
Tony
Yes two versions offered on these Corollas. The DOHC 4AGE, or the SOHC 4AC/3AU.
The twincam is fuel injected, the latter is carb'ed.
From your dyno figure, either you have the SOHC engine, or you're running the Twincam with a blown cylinder or something, unless the dyno is very inaccurate or the powertrain isn't setup properly.
Thanks again for your replies, I will ask my local garage to check out engine compression and check TVIS as advised. The car runs very well and is very quick ( compared to a standard MG Midget ! ), however from your feedback it seems that I should certainly have a few extra hp. I did a track day last year and was quicker than everyone (Midgets, MGB's F's and TF's ), although didn't have the speed on the main straight to get near a K series 140bhp Midget. I have another trackday in May and would like some more power to sort the aforementioned out !!. At the moment all Midget conversions are K series and I think I am looked upon as being a 'traitor', although I certainly wouldn't swap ! Cheers Tony.
Dynos can give very different readings, a 20v silvertop over here put down 63kw@ the wheels on one dyno then 93kw@ the wheels at another. (93kw is normal/good for a facelift ST)
Its all relitive, a dyno is usefull to see increases from modifications but you shouldn't compare results with other engines on other dynos.
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