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This is the first 740 turbo I've owned or driven. Runs very well with only a slight hesitation about 3k when trying to accelerate hard, say for merging.
My question is, the engine is pretty "soft" under about 2500rpm and I'm wondering if they (B230FT) need to be revved out for better than average acceleration? Or am I down on power? Seems like I'm having to go 3/4 throttle shifting about 3k to get away from a light with traffic 'till I'm into third. Between 3k and 4500 power is good. Around 5k power starts to fade. I don't make a habit of running over 4k, btw.
Cruisiing at 55-70 in OD there's adequate reserve for roll-on passing. So, is this engine known as a "torquer" or is she a "revver?"
Does this sound reasonable?
--
Erwin in Memphis, '88 745t 183,000 miles, '95 855t For Sale
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They have more torque than HP. My 760 doesn't have as much pull under 3000 rpms as it does above 3k. From 3000-redline with the turbo spinning the car will pull like a train though.
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1988 760Tic - 155,550 1966 M-B 230 sedan - 98,000 - Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us. - Bill Watterson
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Hmmmmm...."torquer" or "revver"? Well, did ya ever try putting it in 2nd at around 40-55 kph (25-35 mph), tipping your foot into the throttle a bit (get the turbo spinning) and then mashing the throttle? That's probably where you'll get the strongest rush from a B230FT in my experience. It feels like a rocket when you do that, especially if you're going up hill :) Makes the engine feel like a "tourqer". It seems the the most power comes out of my B230FT somewhere around 3300-4800 rpm. Once the engine gets around 5200-5500 rpm, it's power seems to level. I wouldn't worry about revving it, just try to stay below the redline (which I believe is a little conservative at 6K rpm). I don't run mine about 5500 rpm very often. Although, your's has the 9mm connecting rods doesn't it? Might be a *little* different story with them (I'm not sure). Mine has the 13mm rods. My B230FT is "soft" under 2500 rpm too. The engine doesn't have a lot of power when it's off boost. Remember, the B230F only has 114 hp with something like 9.5:1 compression. The turbo engine has 8.7:1 I think, so that means the engine isn't that powerful without boost. I did notice a little difference though after my B230FT was rebuilt (bad piston slap, leaks). It was bored 0.30 over, the head was plained 0.10 and the turbo was turned up a bit (think it's around 9-10psi boost). It seems to have more grunt off the line now. I think that's thanks to the slightly bored pistons. Oh, the piston slap returned to a lesser degree after the rebuild too. Ugh. I guess I have to live with it..... So is the B230FT a "torquer" or a "revver", I'm not quite sure :) Are you down on power? Maybe a *little* at 183K mi (original turbo?). Oh, and the pre-'90s have a different turbo (usually Garret) then mine (Mitsu). Your's is rated something like 160hp and 185 ft-lbs where the '90+ B230FT is rated at around 162hp and 195 ft-lbs. Anyway, does any of this make sense? LOL :)
--
Chris. Halifax N.S. '91 745Ti, 274K km.
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Thanks,
I'll put the parts together to measure actual boost, fuel pressure and compression in the near future. My turbo's a Mitsubishi, not Garrett and yes I do have the K block with the 9mm rods. Another reason I don't venture past 4500 often at 187,000 miles. If a good "big rod" block or engine comes available coincident with funds being available I'll jump on it.
Good point about the lower compression ratio and corresponding lower power output off booost. I'll have to learn to drive around it.
Regards,
--
Erwin in Memphis, '88 745t 183,000 miles, '95 855t For Sale
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How do find out if you have the K motor or not? K motor has the 9mm rods? correct?
--
1988 760Tic - 155,550 1966 M-B 230 sedan - 98,000 - Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us. - Bill Watterson
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Look at the block on the intake side. Just above the second freeze plug there will be a "K" cast into the block. Can't miss it. As to when the larger rods and relocated thrust bearing was (re)introduced, I'm not sure but I think around '90-'91? Turbobricks.com, under Mods and 700/900 turbos, there's a description.
Regards,
--
Erwin in Memphis, '88 745t 183,000 miles, '95 855t For Sale
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Looks like I have the dreaded "K" molded into my block. The date on the block indicates that it was manufactured in '88. After I am done beefing up the cooling system I wouldn't mind a little bit more power and according to Turbobricks the K engine can probably handle my needs.
--
1988 760Tic - 155,550 1966 M-B 230 sedan - 98,000 - Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us. - Bill Watterson
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My '88 745T had a flatter power curve than my '86. The '88 had a mits turbo, the '86 a garrett. The garrett doesn't start to work well until 2500-3K rpm. The mitsubshi started much earlier, let's say 2K-ish, but it felt great- didn't really matter what gear you were in, a decent amount of power was always there. If your '88 has a garret turbocharger, I wouldn't be surprised by your description of the motor's performance. If it has the mits TD04 that mine had, I'd say something is off.
My 2 cents-
-Dylan
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that sounds like my garret..before it was rebuilt, much better afterwards...
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i believe peak HP is acheived at approx 4500 rpm.... I found some performance curves on turbo bricks (I think).. my b230ft is very civilised under 2500 rpm, by 4.5k shes pullling ...of course you also have to remember the turbo lag...
now interestingly...since replacing the dizzy cap & leads and cleaning the TB i have noticed the car feels decidely SLOWER..however a look at the speddo reveals its a fair bit quicker, just the 'turbo' feel has gone away...just a smoooth power flow, so you dont get such a kick in the seat of the pants...
gota remember thats 3000lbs of iron your pushing around....
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