Whats the reason for the difference

[wwe_champion]

Gday all, i just have a question. My mate and i both have 180sx and both have RB20's in them. Mods wise they are very similar in that there isn't really any. But when we are travelling at similar speeds are revs are very different. E.g when im doing 100km/h my car reads out that im doing 4500rpm while my mate at the exact same speed is only doing 3500rpm and they are both in 5th gear. Could anyone tell me the possible reasons for the difference in revs and could this be a problem.

[sewid]

RB20's? Sure you dont have SR20's?

[MJ]

im sure he knows what engine he has

they both got swapped for rb20's by the sounds of it. Sorry i cant help ya mate

[robbo31]

do u have different diff ratios???

[Pekatu]

yeah it would either be diff ratios, gearbox, or you tacho is wrong, my rb20 sits at about 3000 ish at 100kph

[gtrken]

Some Silvia/180sx's had 4.3 diffs and some had 4.1's.

If it is a Jappo dorifto style it may even have 4.4 or 4.6's in it along with an LSD.

Cheers

Ken

[usuckpoo]

another possibility is that you're running ex-auto diff ratios...although im not too sure what the exact ratios are...

[sewid]

im sure he knows what engine he has

they both got swapped for rb20's by the sounds of it. Sorry i cant help ya mate

yeah youd think so, but he said he and his friend have no mods.

why would you go through the effort of swapping the SR20 for the RB20 anyway? If you were going to swap to an RB you would at least go for the RB25.

[blind_elk]

Can we safely assume you are driving side by side, so you know you are both doing the same speed.

sewid - maybe RB20s are a lot cheaper than RB25s.

[MJ]

yeh rb20's are heaps cheaper then rb25's

and they might not have been sr20's they could have started life as a ca18 which was getting old. Yeah now i think of it if the car was auto it will have a different diff ratio too.

[wwe_champion]

would it be best if i could get the ratio changed? Who is best to do this?

[Mrman]

Why would you want to change it. If you have an auto diff ratio and your car is manual it means you will have a quicker take off then your friends car.

[wwe_champion]

In actual fact his is quicker, why i don't know they are roughly both running on same psi, but his definitely is quicker.

[dojobi]

Just to check that the tacho isn't wrong (as 1000rpm seems like a huge amount more for a 4.3 diff over a 4.1 one), do the engines sound the same when they cruise at that speed? I mean does your one actually sound like it's doing 1000rpm more than his? Since yours is slower, it does sound like your diff isn't some super high ratio one.

[wwe_champion]

Im not the most knowledgeable when it comes to the mechanical side of cars, but can someone please explain what the difference is with the diff ratio and how it effects the car. Is it related to the gear ratio. Im sorry if this is a dumb question but i don't really know. Tah