I've been eyeing turbocharging as a potential future upgrade to my rather sluggish 528e. I've seen a lot of mouth watering performance figures and dyno charts, but I wanted to ask you guys who've been driving them for a bit a couple questions I hadn't seen answers to.
Gas mileage: pretty self explanatory, what kind of gas mileage are you guys actually seeing, driving around with the turbochargers.
Noise: Obviously adding a different induction system is going to change the sound of the car somewhat. Would that sound make the car less pleasant to drive as a daily driver?
Turbo Lag: the mystical turbo lag. Is it noticeable in your car? where do you feel like power picks up in terms of RPM?
Gas mileage and driveability
I experience better than avaerage milage than other E24s, about 24mpg. Cruising on the highway I get around 26-27mpg.
Properly designed noise at cruise is minimal... nice and strong while taking off and accelerating hard.
Lag?... what's that? Unless you can perceive picoseconds don't worry about it in a well designed system.
Where power comes in has many, many variables...
Properly designed noise at cruise is minimal... nice and strong while taking off and accelerating hard.
Lag?... what's that? Unless you can perceive picoseconds don't worry about it in a well designed system.
Where power comes in has many, many variables...
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Bill in MN
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I don't normally check mileage since I really don't care. It's too hard to keep my foot out of the gas and that's not conducive to good economy. I did experience 22 from a tank of highway running with the motor running pretty fat.
Noise at cruise is pretty normal but there's a lot more under acceleration. There's nothing like the sound of a turbo spooling up and a free flow exhaust letting it all out!
As for lag? Ditto Sweeney. Not much at all.
Noise at cruise is pretty normal but there's a lot more under acceleration. There's nothing like the sound of a turbo spooling up and a free flow exhaust letting it all out!
As for lag? Ditto Sweeney. Not much at all.
Wow, that's pretty much exactly what I wanted to hear. I'm curious though about the better than average gas mileage. That seems sort of backwards to me, it seems like a turbocharger should consume more gas than the same naturally aspirated engine. Not that I'd complain, I was mostly just making sure that it wouldn't give my car SUV-like fuel consumption. Is similar to better than NA gas mileage pretty normal for people?
my turbo 5 has a 2.93 in the rear and I get really good milage and low revs at high speeds. At least from the neighborhood trips. You can get almost anywhere through just backstreets and never see a cop. 
I got a 3.25lsd commin soon so the revs will jump a little, but the traction...... 
that will be worth it.
The lower diff really helps, my old nissan had a 4.11 rear end and i was turning like 3600rpms at 60mph. Made boosting the turbo in 5th gear not a problem. I never had to downshift. Just floor it and watch the happy gauge. I havent brought my turbo 5 onto the highway yet to see what she can do. Soon. Very soon.
I got a 3.25lsd commin soon so the revs will jump a little, but the traction...... that will be worth it.The lower diff really helps, my old nissan had a 4.11 rear end and i was turning like 3600rpms at 60mph. Made boosting the turbo in 5th gear not a problem. I never had to downshift. Just floor it and watch the happy gauge. I havent brought my turbo 5 onto the highway yet to see what she can do. Soon. Very soon.
My car runs 17mpg. But my engine is kinda used up and I have been runing the car open loop for 3 years now for tuning purposes. I believe the low milage has some to do with that, plus lots of boost.
The lag is mostly percieved on were the power "builds" fastest. In the E28, the turbo systems out there make more torque almost every where in the rpm range over the NA cars. The lag is a "feel" issue because the car makes most of the torque gains in the 3-4k rpm range. Thats were the car comes on cam. To explain, going WOT at 2.5k RPM, the car starts making boost imediately, but really makes ~70% of the torque gains from 3-4k. From there the torque falls off but not fast enough to stop making hp. At ~5200rpms, the hp starts to fall also. So the power surge(as I like to call it) in the 3-4k range is percieved as lag, when its not, its power gain....
RussC
The lag is mostly percieved on were the power "builds" fastest. In the E28, the turbo systems out there make more torque almost every where in the rpm range over the NA cars. The lag is a "feel" issue because the car makes most of the torque gains in the 3-4k rpm range. Thats were the car comes on cam. To explain, going WOT at 2.5k RPM, the car starts making boost imediately, but really makes ~70% of the torque gains from 3-4k. From there the torque falls off but not fast enough to stop making hp. At ~5200rpms, the hp starts to fall also. So the power surge(as I like to call it) in the 3-4k range is percieved as lag, when its not, its power gain....
RussC
How would one fix this? the S38 at least builds power right on up to 6500 rpm, stock. I'd imagine just a touch of light work would move the HP peak to the 7000 range..russc wrote: At ~5200rpms, the hp starts to fall also
Turbo motors typically dont need bigger valves or any of the other NA tricks. Can the 12v head just not move enough air above 5200 rpm?
From my understanding it is a couple of things. First off you are correct, the head can only flow so much, and once you get above 5200 or so, it starts choking. The second thing is, and this is more for an NA motor is that the cam is not designed for the high RPM power numbers. Now this can also effect the turbo setup if the cam is bad enough, but I really don't think the stock one is that bad. Lastly, it has to do also with the turbo sizing. A larger turbo makes boost at higher RPM, but has more lag. The smaller turbo makes boost at lower RPM, has less lag, but also will start to over rev at higher RPM. So all in all when you look at why an S38 makes power higher up in the rev range, you can attribute it to more air flow, and more cam.
From my personal knowledge, if you were to run larger valves and more lift in a turbo motor you will be able to move the power band higher. This is because you won't run into choke flow as quickly. But you have to remember that you need to size the turbo correctly for the RPM band that you want to make power. Lastly, you also want to make sure you have the correct cam for the job. Turboing the stock motor will allow you to keep the NA torque down low, like Russ said but will boost the motor up top. Like Russ was saying if you size the turbo right, etc it should be a seamless transition. It should feel like a stock E28 535i just that when it comes on cam, it has a lot more power. There are people out there that make a ton of power, but the motor just isn't driveable. The real question becomes what type of car do you want, extreme power, or good driveability.
Hope this helps, and please correct me if I am wrong, I don't have my reference materials in front of me right now and I am doing this all from memory.
From my personal knowledge, if you were to run larger valves and more lift in a turbo motor you will be able to move the power band higher. This is because you won't run into choke flow as quickly. But you have to remember that you need to size the turbo correctly for the RPM band that you want to make power. Lastly, you also want to make sure you have the correct cam for the job. Turboing the stock motor will allow you to keep the NA torque down low, like Russ said but will boost the motor up top. Like Russ was saying if you size the turbo right, etc it should be a seamless transition. It should feel like a stock E28 535i just that when it comes on cam, it has a lot more power. There are people out there that make a ton of power, but the motor just isn't driveable. The real question becomes what type of car do you want, extreme power, or good driveability.
Hope this helps, and please correct me if I am wrong, I don't have my reference materials in front of me right now and I am doing this all from memory.
Rob, What do you consider "extreme" power? Our TCD cars produce pretty violet acceleration on demand yet exibit as good if not better drivability than stock. In snowless conditions mine does duty as my commuter car about 80 miles per day.
Matt, When you have a lot of torque you can use higher gearing and you don't need to wind the engine out.
Matt, When you have a lot of torque you can use higher gearing and you don't need to wind the engine out.
I think Rob is reffering in general to big hp cars, like in the 750hp range and up. At that point you start sacraficing some drivability to get that kind of power. IMHO, the M30b34 is very driveable well up into the 450whp range, but you gotta spend some money to do that. Blackie is a good example of that
As Rob said, its all a comprimise of where you want to make power. 2v/cyl engines make good low end torque, 4v/cyl engines make good top end hp. Which do you want????
Now, you can up the hp in the rev range on the M30 by camming, larger turbo and head work. But your not going to get it to make power at 6600rpm like a S38. Not unless you want to go to a 300deg+ cam, now your really going to sacrafice drivabily with that, and it won't work that well under boost either.
RussC
As Rob said, its all a comprimise of where you want to make power. 2v/cyl engines make good low end torque, 4v/cyl engines make good top end hp. Which do you want????
Now, you can up the hp in the rev range on the M30 by camming, larger turbo and head work. But your not going to get it to make power at 6600rpm like a S38. Not unless you want to go to a 300deg+ cam, now your really going to sacrafice drivabily with that, and it won't work that well under boost either.
RussC
Well, all that having been established, I think I'm sold on turbocharging rather than an engine swap (I was thinking maybe an s52 swap, which I gathered would be about the same cost as a high quality turbo kit) what kind of power could I expect to pull out of my super-eta? I didn't see a dyno for an eta at turbocharging dynamics. I understand that there are a lot of factors, but how about a general range, and roughly the cost and equipment required for it.
Sure. But subjectively, winding the engine it feels "funner" to me. A Supra TT 6 speed has a 7k rpm redline and the gears are nice and close.. a redline shift from 2->3 leaves you at about 5k, where the 2nd turbo has just spun up (its 4xxx something). That 2->3 gear change is a beautiful thing.Sweeney wrote:Matt, When you have a lot of torque you can use higher gearing and you don't need to wind the engine out.
i dont think a radical cam is what i'd want to do on a turbo car... if one got a larger, laggier turbo, would that help the power keep building at higher RPM? assuming no head/cam/valve work, is turbo sizing sufficient to move the power band around ?
I understand that high boost at low rpm is easier on a motor than no boost at high rpm.. but man..high RPM just feel great
A M30t will never feel like a Supra TT, or a ///M5 for that matter. It just won't breath at high rpm like those engines. Just using a larger turbo on a M30 will not make a significant change in the power band by itself, sorry. And your right, a large cam(more than ~280 deg) is not the best way to go with a M30 turbo, trust us. Well, unless your building a dedicated track car.Matt wrote:Sure. But subjectively, winding the engine it feels "funner" to me. A Supra TT 6 speed has a 7k rpm redline and the gears are nice and close.. a redline shift from 2->3 leaves you at about 5k, where the 2nd turbo has just spun up (its 4xxx something). That 2->3 gear change is a beautiful thing.Sweeney wrote:Matt, When you have a lot of torque you can use higher gearing and you don't need to wind the engine out.
i dont think a radical cam is what i'd want to do on a turbo car... if one got a larger, laggier turbo, would that help the power keep building at higher RPM? assuming no head/cam/valve work, is turbo sizing sufficient to move the power band around ?
I understand that high boost at low rpm is easier on a motor than no boost at high rpm.. but man..high RPM just feel great
RussC
The only way to change the overall shape of the torque curve is to change the cam. Different turbo sizes and types can come on at varying points in the low to mid range, but they'll all fall off at a very close point on the top end given the same cam.
You don't need to go radical to change this. A stock 260 cam will do as Russ says. A 264 cam from the m30b35 will sacrifice a bit of midrange and pull a little better up top, and a 272 from the m30b32 will make torque higher in the rpm range than either of the other two.
Jeremy
You don't need to go radical to change this. A stock 260 cam will do as Russ says. A 264 cam from the m30b35 will sacrifice a bit of midrange and pull a little better up top, and a 272 from the m30b32 will make torque higher in the rpm range than either of the other two.
Jeremy
General agreement is that the cams are labeled like this:
m30b34 "green" w/motronic = 260
m30b34 "dirty" & m30b35 = 264
m30b32 w/motronic = 272
If you look at the torque curve from a 533i, this makes sense. That motor makes hp all the way to a 6k redline. The peak hp of 181hp (IIRC) is rated at 6k rpm for that motor. The m30b34 makes 182 at 5250rpm or thereabouts but falls off after.
The profile for the BMW m30b32 cam is not in that chart, unfortunately, so I have no idea what the "real" specs are.
Jeremy
m30b34 "green" w/motronic = 260
m30b34 "dirty" & m30b35 = 264
m30b32 w/motronic = 272
If you look at the torque curve from a 533i, this makes sense. That motor makes hp all the way to a 6k redline. The peak hp of 181hp (IIRC) is rated at 6k rpm for that motor. The m30b34 makes 182 at 5250rpm or thereabouts but falls off after.
The profile for the BMW m30b32 cam is not in that chart, unfortunately, so I have no idea what the "real" specs are.
Jeremy
I guess I phrased that poorly, I was more looking for total costs in the event that someone recommended something like a custom cam or lightened flywheel or something that wasn't immediately listed there, or even the need to add certain items like a custom exhaust or the wastegates and manifolds and such which are listed separately from the kits.The cost of the kit is at TCDs site!
I'll apologize if this has been discussed already, but the search function is still sort of hit and miss from the website changing the other day. Are these levels of boost a ballpark of what is easily and safely acheivable with just a stage 1 kit, or would I need the addition of an intercooler or other upgrades to develop/handle it? I didn't see find any figures on what kind of boost levels these kits can give . It would be swell to be pulling 300+ lbs of torque out of my car.At 14psi, you can expect a dubbling of power on that engine. So take stock power, x2. If 7psi, x1.5 etc.
From what I'm reading here, it sounds like the low redline of my eta (it's a little above 5000, 5200 maybe?) wouldn't have much effect on the turbo since it's right around there that the turbo stops developing more power, is that right?
Nope, the turbo won't stop developing the power - it's that the engine will. Hence this whole cam discussion - after 5200 or so RPM, the cam lift blah blah isn't enough to continue to increase horsepower at those revs - so HP will begin to decline (unless using the 533i cam which pulls you to 6 grand nicely). The only time the turbo stops putting out power is if it's undersized for the engine size or boost level you're trying to run.From what I'm reading here, it sounds like the low redline of my eta (it's a little above 5000, 5200 maybe?) wouldn't have much effect on the turbo since it's right around there that the turbo stops developing more power, is that right?
Right, but that dyno is with a p/p head. Id like to see a stock b32 dyno. Have to keep looking.Jeremy wrote:Todd has a couple from when he had the worked 733i turbo car. I looked around but couldn't find any, sorry.russc wrote:Do you a dyno plot of a b32? Would be iteresting to see.
RussC
Jeremy
PS - on topic, my car with 3.46 and running ~10psi of boost returns 22-25mpg on the highway.
RussC
My build is slowly coming together.... key word is slowly...
I ordered that b35 head with b33 cam from Ray a few days ago, I expect it should be in sometime soon -- even if not -- no worries, it'll come waaaaaay before the build anyway.
But I'm totally ready to see what benefits the combo of the two will yield!
I ordered that b35 head with b33 cam from Ray a few days ago, I expect it should be in sometime soon -- even if not -- no worries, it'll come waaaaaay before the build anyway.
But I'm totally ready to see what benefits the combo of the two will yield!