LSD in 230hp RWD car
Discussion
BMW Compact with 330i engine.
Lots of people bang on about getting an LSD. I've been recommended going plate for a RWD car. Gripper LSD has been mentioned.
For a car with 230hp is it worth the outlay?
I'm no Lewis Hamilton but if its a magic pill to track day driving I'm not opposed to splashing out.
The car is in the process of being built so I've got the engine going in along with clutch etc. I was kinda thinking about using it for a year and seeing what I think but as the cars in bits now might be the right time to add one.
What do you think?
Lots of people bang on about getting an LSD. I've been recommended going plate for a RWD car. Gripper LSD has been mentioned.
For a car with 230hp is it worth the outlay?
I'm no Lewis Hamilton but if its a magic pill to track day driving I'm not opposed to splashing out.
The car is in the process of being built so I've got the engine going in along with clutch etc. I was kinda thinking about using it for a year and seeing what I think but as the cars in bits now might be the right time to add one.
What do you think?
Darranu said:
Yes is the short answer, I've had my E36 328 track car for 10 years now and the LSD was one of the first upgrades.
Would not have it any other way, makes any slide predictable and consistent whilst giving that extra drive out of tight corners when the inside wheels unloaded.
My experience is with adding a Quaife LSD to a 155bhp FWD car, but very similar to above, plus more predictable on wet, bumpy and poor road surfaces.Would not have it any other way, makes any slide predictable and consistent whilst giving that extra drive out of tight corners when the inside wheels unloaded.
Back when i was on budget road tyres, yes, an LSD would have been useful. However, on decent sticky track tyres, they dont ever lose traction, so havent seen the need for an LSD any more.
So id say get decent tyres first, then see if you can still spin wheels. My 3.0 Z4 with 255 width federal 595 rsrs at the rear couldn't.
So id say get decent tyres first, then see if you can still spin wheels. My 3.0 Z4 with 255 width federal 595 rsrs at the rear couldn't.
brillomaster said:
Back when i was on budget road tyres, yes, an LSD would have been useful. However, on decent sticky track tyres, they dont ever lose traction, so havent seen the need for an LSD any more.
So id say get decent tyres first, then see if you can still spin wheels. My 3.0 Z4 with 255 width federal 595 rsrs at the rear couldn't.
Yes I was going to ask the OP what tyre he will be running and how much weight he will be saving compared to std. Keeping it relatively heavy, while not desirable, will help traction and perhaps reduce the need for a LSD. Having said that, it would probably still massively need it in the wet irrespective of those parameters. So id say get decent tyres first, then see if you can still spin wheels. My 3.0 Z4 with 255 width federal 595 rsrs at the rear couldn't.
this might be me being a wuss, and will hand in my pistonheads card on my way out, but...
i actually quite like not having an LSD when doing wet trackdays... for example, Bedford autodrome is an absolute ice rink when it rains, and just looking at the throttle funny is enough to spin the car exiting the many hairpins. having an open diff gives me half a chance of just spinning the excess power away through one wheel, rather than constantly dealing with oversteer.
as i say, i'll hand in my pistonheads card on the way out...
i actually quite like not having an LSD when doing wet trackdays... for example, Bedford autodrome is an absolute ice rink when it rains, and just looking at the throttle funny is enough to spin the car exiting the many hairpins. having an open diff gives me half a chance of just spinning the excess power away through one wheel, rather than constantly dealing with oversteer.
as i say, i'll hand in my pistonheads card on the way out...
Muzzman said:
Sounds like I will be getting a LSD :-)
Another question, its been suggested I get a lower final drive when installing the LSD. I'm not that technically minded what will this do and how do I work out what to buy?
Most road cars are very overdriven in top gear for economical and quiet running on a motorway ie 3500 revs in top is 80mph, if the engine redlines at 7000 revs that gives a theoretical top speed of 160mph but the cars top speed is probably only 135 because it hasn't got the grunt to pull maximum revs in top.Another question, its been suggested I get a lower final drive when installing the LSD. I'm not that technically minded what will this do and how do I work out what to buy?
When I tracked a Clio 182 it would reach 120mph in 4th, somewhere like Silverstone on the Hangar straight that was three quarters of the way down the straight so you put it in 5th but it stays at 120 as it hasn't got the torque to accelerate any further.
You have a 5 speed gearbox but on most tracks you only use 2nd, 3rd and 4th which is inefficient. In a purpose built racing gearbox in something like a Westfield 1st gear is often very "long" good for say 50mph so can be used at a tight hairpin, 2nd, 3rd and 4th are evenly stacked and 5th is calculated with the diff ratio to give a top speed of maybe 130 mph which is all you are likely to achieve on most tracks anyway so you are using all 5 gears and can keep the revs better in the power band. A serious racer might change diff ratios to alter the top speed for different tracks ie lower top speed at Cadwell or Brands Indy and higher for Silverstone or Snetterton.
In your example you are likely to be using a standard gearbox but as you say you can change the diff ratio when you fit an LSD, if your theoretical top speed is 150 mph with a 3.7 to 1 diff ratio, if you fit a 4.2 ratio that is a 14% change so will reduce your top speed to 129mph but improve your acceleration out of corners and allow you to use more of the gears.
Hope that makes sense, I stand to be corrected on my maths but think I have the principle right, people with more knowledge of BMWs may know what your standard diff ratio is and what others are available.
almost certainly yes to both lsd and lower fd if you want to enjoy driving the car more. few cars in the last 15 years have been geared for driver involvement! i can't comment on the exact numbers for the fd, maybe the owners forums can help. be wary of some of the more aggressive ratios unless you just want a noisy car when cruising, but some reduction is beneficial. consider the torque curve, it's quite flat in the 330?
Pretty much covered above, fit a final drive with a higher number and you will accelerate faster, use more gears. The ideal is to top out jin 5th ust before the braking point at the end of the highest speed section you're likely to come across - aside from Silverstone GP that's likely to be Snetterton Hangar Straight.
If you're not going to either of those tracks you might be able to run a higher ratio final drive, but it would be revving pretty high at motorway speeds; as you want to keep it relatively civil you probably wouldn't like the noise due to revs when driving to and from the track, or using it anywhere else.
Best thing is to find out your final drive ratio, gear ratios, tyre size and engine rev limit, and plug them into an online gearing calculator. It'll give you your current top speed and speed in every gear. Then just change the final drive ratio (I'd start by looking on ebay for the ratios fitted to existing BMW LSD-equipped diffs) and see if anything looks right.
As someone said above, about 130mph is going to be the upper end of what speed you'd achieve with ideal gearing on a <1ton car and 230bhp on even the fastest tracks in the UK so perhaps that's a decent number to aim for as a ballpark, then think about what tracks you're using the car on, how far away they are, and make your choice based on acceleration and target top speed vs ensuring it's bearable on a motorway.
If you're not going to either of those tracks you might be able to run a higher ratio final drive, but it would be revving pretty high at motorway speeds; as you want to keep it relatively civil you probably wouldn't like the noise due to revs when driving to and from the track, or using it anywhere else.
Best thing is to find out your final drive ratio, gear ratios, tyre size and engine rev limit, and plug them into an online gearing calculator. It'll give you your current top speed and speed in every gear. Then just change the final drive ratio (I'd start by looking on ebay for the ratios fitted to existing BMW LSD-equipped diffs) and see if anything looks right.
As someone said above, about 130mph is going to be the upper end of what speed you'd achieve with ideal gearing on a <1ton car and 230bhp on even the fastest tracks in the UK so perhaps that's a decent number to aim for as a ballpark, then think about what tracks you're using the car on, how far away they are, and make your choice based on acceleration and target top speed vs ensuring it's bearable on a motorway.
For me, considering the cost of the diff in relation to the value of the car would be a factor. Used locker from a 328i Sport probably very different to going to Quaife for brand new. Over the years I have spent far too much on cars when I would have been better off upgrading the whole car...
I definitely notice an LSD on track. That said, I am also comfortable in RWD cars without them, and simply drive around the open diff. As said above, sticky tyres can help and also not getting on the power too early.
I definitely notice an LSD on track. That said, I am also comfortable in RWD cars without them, and simply drive around the open diff. As said above, sticky tyres can help and also not getting on the power too early.
Not sure what you mean by drive around the open diff? It's not a problem per say, it's a configuration which in "some" circumstances is more limited than an LSD configuration, you drive the machine to its limit, but different setups have different limits and you won't exceed the limit of an open diff with driving technique.
Many factors to consider for OP. If your setup is very stiff (very little to no roll like a racer) and you over tyre the car, then arguably LSD will only be an advantage in the wet. Else, as stated above.
For reference, I have an E36 328 with 220-230ish HP. Started OEM open diff, 2.93 ratio, geared for over 165mph in top gear, e.g battle ship acceleration. Drove it like that for a while and whilst fun with my setup of soft cheap coilovers putting power down out of hairpins got old as the revs go up but you go nowhere. Got a plate LSD cluster rebuilt with some upgrades and 40% lock, a 3.23 CW&P and all the associated bearings and seals and had the diff rebuilt (total cost around 1K Inc labour). The change in my setup was obvious, more grip on low speed corner exits, faster lap time, obviously much better acceleration (more like destroyer now) with the 3.23FD and whilst this setup is still geared to 150ish (not maximising acceleration) it's a balance as now 5th gear at 60mph is around the 3Krpm mark, so motorway driving is just bearable in noise and fuel consumption to and from track. Any higher than that and it probably best be on a trailer imo.
Decreasing wheel/tyre circumference will increase rpm and indicated speed (over reading on Speedo), but you won't actually be going any faster on GPS.
All depends on the setup you are going for and what compromises you are willing to make. My E36 is a dedicated caged track car, it doesn't do anything else but that now, wouldn't want it to with the current setup as too compromised for road use now.
Good luck.
Many factors to consider for OP. If your setup is very stiff (very little to no roll like a racer) and you over tyre the car, then arguably LSD will only be an advantage in the wet. Else, as stated above.
For reference, I have an E36 328 with 220-230ish HP. Started OEM open diff, 2.93 ratio, geared for over 165mph in top gear, e.g battle ship acceleration. Drove it like that for a while and whilst fun with my setup of soft cheap coilovers putting power down out of hairpins got old as the revs go up but you go nowhere. Got a plate LSD cluster rebuilt with some upgrades and 40% lock, a 3.23 CW&P and all the associated bearings and seals and had the diff rebuilt (total cost around 1K Inc labour). The change in my setup was obvious, more grip on low speed corner exits, faster lap time, obviously much better acceleration (more like destroyer now) with the 3.23FD and whilst this setup is still geared to 150ish (not maximising acceleration) it's a balance as now 5th gear at 60mph is around the 3Krpm mark, so motorway driving is just bearable in noise and fuel consumption to and from track. Any higher than that and it probably best be on a trailer imo.
Decreasing wheel/tyre circumference will increase rpm and indicated speed (over reading on Speedo), but you won't actually be going any faster on GPS.
All depends on the setup you are going for and what compromises you are willing to make. My E36 is a dedicated caged track car, it doesn't do anything else but that now, wouldn't want it to with the current setup as too compromised for road use now.
Good luck.
Edited by Humour on Wednesday 31st March 15:47
If you can get an LSD easily and cheaply to drop in from another BMW you absolutely should - your car will be easily powerful enough to enjoy the benefits (not talking about big power slides).
Changing the final drive and/or getting an aftermarket lsd are perhaps things to consider further down the track.
Changing the final drive and/or getting an aftermarket lsd are perhaps things to consider further down the track.
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