Tach accuracy to revlimiter

[jayuuey]

Finally drove the s50 to upper rpms today. I read that the stock revlimiter was 6250 but when I took it up, I ran out of Tach and it still felt like the car was pulling. The dme looked untouched but I never opened it to verify. I'm thinking maybe the Tach isnt accurate after a certain point. Does this sound right.

Also, is the s50 all top end? I was unimpressed below 5k. Still more power than the m20 but damn up top was pretty exciting. I backed off just below 7k since I wasnt sure how far it would go.

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[pazi88]

As far as know the rev limiter in s50 is past 7000. It's at 6500 even in normal m50 engines.

[TobyB]

Below 5k, the S50 is mostly an M20 stroker, (think, eta)

he quips, heretically...

t

[mtech325]

Interesting post about the power delivery of the S50 being up top. I thought stock redline for the S5x engines was around 6800 rpm if I’m not mistaken. My e30 has an S52 and seems to behave similarly to yours. My friend has an S52 car as well but his car seems to have some better low-end grunt than mine. Both cars are OBD1 converted and have a ZF paired with ~3.25 diffs, but his car does have the OBD2 headers (whereas I still have the cast iron units).

My e36 also has an S52 in it as well (albeit OBD2 with the OBD2 intake manifold, headers & midsection) with a ZF and 3.23 diff, and it seems to pull stronger off the line than my e30, despite being ~400lb heavier and having a dual mass flywheel. So I’m led to believe a proper exhaust system helps on the swap cars too (It seems 2.5” is the popular setup for the single pipe sections).

Is the Vanos in good shape? Might be something to look into as you can rebuild them for not too much with the Besian kit.

[pazi88]

Interesting post about the power delivery of the S50 being up top. I thought stock redline for the S5x engines was around 6800 rpm if I’m not mistaken. My e30 has an S52 and seems to behave similarly to yours. My friend has an S52 car as well but his car seems to have some better low-end grunt than mine. Both cars are OBD1 converted and have a ZF paired with ~3.25 diffs, but his car does have the OBD2 headers (whereas I still have the cast iron units).

My e36 also has an S52 in it as well (albeit OBD2 with the OBD2 intake manifold, headers & midsection) with a ZF and 3.23 diff, and it seems to pull stronger off the line than my e30, despite being ~400lb heavier and having a dual mass flywheel. So I’m led to believe a proper exhaust system helps on the swap cars too (It seems 2.5” is the popular setup for the single pipe sections).

Is the Vanos in good shape? Might be something to look into as you can rebuild them for not too much with the Besian kit.

All that is explained by your engine setups. The bigger displacement in s52 makes more torque at the low end compared to s50. Also the obd2 intake makes lot more torque at the low end compared to obd1 one and transferring it to top end power. Same thing with the headers. So in summary. If you wan't your car leave the line as your friends car does. Use obd2 parts.

[jayuuey]

I'm using a the g260/3.73 and a pretty much stock obd1 full exhaust. I'm hoping to switch to obd2 exhaust mani/midpipe at some point. I had a 99 m3 and was hoping for a similar power band. If little exhaust tweaks can really bring some torque, it would be worth it. I feel like e30 s50 has to be rung out to put a smile on my face. Then again only had 10 mins seat time so far.

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[TeXJ]

any update on this? Have you changed the exhaust?

[jayuuey]

I replaced the vanos and the power is felt from idle to redline. If your engine feels peaky, definitely check your vanos seals. I'm very pleased with the swap performance now. I still may try the obd2 midpipes at some point but its great as is.



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