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jon dee

How much boost do the new BM's run ???

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I was looking at the hp figures being quoted for the latest 3 litre turbo engines and got to thinking where does the extra 200hp come from between my 2008 N54 and the latest 2021 competition engine. It's a fair jump from 300hp to 500hp and while improved engine design and fuel delivery etc can account for some, most of the increase must come from more boost. A stronger fully forged engine can obviously take more boost.... but how much was it being fed ?

Being curious, I did a bit of digging and saw figures as high as 32psi being bandied around !!!!!!!

While by no means extreme for highly modified cars, I did think that was on the high side for a factory production car, so I dis a bit of digging and found the chart shown below. This shows a pull through the first three gears on an X3M Competition with the S58 engine. That shows boost reaching into the low 20's which is entirely believable. If AIT is ambient temperature then it was a hot day which would likely have caused the DME to pull a bit of timing. Under ideal conditions I could see this engine topping out at 24-25psi around peak torque.

Does anyone have boost figures for the earlier twin turbo M3's  that were running around the 400hp mark ? What about people running upgraded turbos on the N54 ? Rumour has it that the 2021 M3 with the nose job has more up its sleeve, so it will be interesting to see what can be done with a methanol mix and water injection :)

Cheers,,,

bmw s58.jpeg

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Hey John,

I am running 21 psi with 17t turbos making 460whp and 690nm at the engine. This is on an a built bottom end n54 with 9.5:1 compression. Unsure of timing. 

 

Edited by Ninjaspartan

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Good numbers Jordan !!! Are you using the factory DME with a flash tune ? Don't see much information around about aftermarket ECU's for BM's.

Cheers...

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From a quick Google, the S55 is 18psi, or 20 in the Competition spec.

Although I'm not sure PSI really tells the whole story, I think a larger turbo and piping would push more air with less PSI (don't shoot me if I'm botching the physics here). 18PSI from the stage 2+ tune in my N55 335i didn't give quite the same thrust as my stock M4, I doubt that was cracking the 400hp mark.

Edited by Matth5

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For sure there are a lot of factors that influence how much power a boosted engine will make. If there are restrictions in the inlets or outlets, removing the restriction will allow the engine to make the same power at less boost. Or more power at the same psi if you prefer :) However, the phrase "turning up the boost" is how tuners extract more power once the hardware is settled and installed. Within reason, more psi will equal more power. Optimising the system requires careful assessment of all the many factors and making the total system from intake to exhaust as efficient as possible, and this is what the BM engineers will spend their time on.

Factory turbos will usually roll over short of redline for good reasons... and to get the driver to change gear before rev cut :) Putting a larger turbo on will allow the engine to stay on boost longer and make more power by virtue of holding the torque curve to redline. That larger turbo will have the potential to to make more psi but if boost is limited by the wastegate then it will push more air at the same psi to hold full boost to higher rpm. Possible downside is that the larger turbo may not be as efficient or spool up as early as the original smaller turbo.

That is just how I see things working. Having two small low mounted turbos on the N54 with tortuous inlets and outlets is an OEM packaging solution. For real power you need to make room for a healthy top mount...

Cheers...

Screenshot_2021-03-19 IMG_4934_e80bfce6-4b7c-4406-b5d7-363c2b853bf9_480x480 JPG (WEBP Image, 480 × 480 pixels).png

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On 3/18/2021 at 12:44 PM, Ninjaspartan said:

Yup. Factory dme with custom tune. Using MHD to flash the tune. 

Are you running e85 or an e85 mix ? I'm getting 17psi on BP98 and an MHD 1+ tune. If I used the car every day I would be keen to try a e30 mix just to see what difference it makes on a pretty much standard car. But it seems that there can be problems if you let ethanol sit in car when it does not get a lot use (or you don't flush it out with gasoline when you are done playing) so that is on the back burner at the moment.

Cheers...

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8 hours ago, jon dee said:

Are you running e85 or an e85 mix ? I'm getting 17psi on BP98 and an MHD 1+ tune. If I used the car every day I would be keen to try a e30 mix just to see what difference it makes on a pretty much standard car. But it seems that there can be problems if you let ethanol sit in car when it does not get a lot use (or you don't flush it out with gasoline when you are done playing) so that is on the back burner at the moment.

Cheers...

Hi John

Its just tunned for Gull 98. So e10 technically. I have looked at the idea of mixing fuels to get e30 as there looks to be a significant gains to be made. But in my case I'm planning to go water/meth as it would be easier than mixing fuels.

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Yeah... the e30 route seems to give a decent lift in power whereas the W/M injection is more about charge cooling and det suppression to allow more timing. I used a Aquamist HSF3 kit on my Corolla when I was running a twinscrew supercharger without any intercooler. MAT would climb past 100degC pretty quick when hauling so I was spraying 50/50 water/meth from around 5psi ramping up with the injector duty cycle.

That kept the MAT under control so that I could tune fuel and ignition maps without having to use all sorts of corrections. I did notice that I could take fuel out of the map in the region where the W/M injection was active. So the meth does appear to add some fuel to the combustion process. Never compared it with just injecting straight water, so can't say if that would have had the same effect.on AFR's.

Cheers...

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I used to mix e85 and 98 to get around e40 but I have a flexfuel kit installed.

Now gull has stopped selling e85 I can only find it at ~4 dollars a litre if bought in 200l drums. 

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3 hours ago, andrewm said:

I used to mix e85 and 98 to get around e40 but I have a flexfuel kit installed.

How did you find the e40 mix compared to straight 98 performance wise ? Worth the hassle ?

Cheers...

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3 hours ago, jon dee said:

How did you find the e40 mix compared to straight 98 performance wise ? Worth the hassle ?

Cheers...

I was running NA on my c63 but yes with a tune it was getting full timing around e35, was pulling timing a little on e20 and a bit on just 98.

US dynos were showing 5-7% HP gain running e40 vs 98 (US 93) and I could tell the difference, expect it only to be more significant on a turbo car.

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MHD1+  335i N54 tune guidelines are indicating around 10whp gain when stepping up from BP98 to an e30 mix. A little more if going to e40 which is the highest recommended on stock fuel pumps. That is on a 330-340whp BP98 base 1+ tune base, so around 3% increase in power. More ethanol will give a higher % increase but when I factor in the cost of upgraded fuel pumps and the possible downside of having ethanol sitting in a car that doesn't see everyday use, I'm not convinced that it is something I want to pursue at the moment.

The MHD OTS tunes are bound to be conservative as they are sold to the public at large. I suspect that a custom tune would likely produce a 5% power increase without adding any ethanol. However, I am really happy with the 1+ tune and won't be messing with it unless I add a few more bolt-ons :) 

Cheers....

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Back on topic :) Here is a guy who is a bit of a rarity on youtube... he actually knows what he is talking about !!! Here he is comparing the S58 in his new G80 M3 Competition to the N54 in his old e90 335i. One of the more interesting facts he talks about is that the new engine has dropped the compression ratio to allow the engine to run higher boost... as much as 25psi. Trade off is a bit less down low for a bit more up top.

Recommended watching for the engine nerds :) 

Cheers...

 

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PSI is a measure of restriction, so really isn't worth reading in to, too much. 

As an example a 2jz toyota I tu-tu with is making 730whp on 23psi. 

The same car, with a different turbo and divider on the manifold was making ~580whp (same dyno) on more boost, with lots less torque and far worse response

 

CFM in to the engine, exh turbine pressure and cylinder head design are the key elements here. 

You will find the general majority of OE turbos are quite inefficient and only work okay through the mid range 

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Yes, there is no doubt that it is possible make a lot of power with less boost when the engine builder is free to optimise the intake and exhaust for maximum flow and low resistance. Get a high tech turbo, run it in its sweet spot and give it all the fuel it wants. That kind of setup will blow away an OEM setup that has dozens of design goals it has to meet for fuel economy, drivability, emissions, noise and so on, as well as producing acceptable performance over a wide rpm range.

Basically, OEM is always going to be a huge compromise for any car sold to the masses. But technology marches on and specific output is increasing at a remarkable rate. Cars like the BM are controlled by computers and the driver has (partial) charge of the computers. Soon the car will take over the driving role and apart from telling it the required destination, there will be no user input. Lawmakers will be happy because they will have absolute control over vehicle speed, accidents will be eliminated  and your safety will be assured. Covid... take me now :(

Cheers...

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 I didn't realise the S58 was 9.3:1. I lowered the compression on my n54 to try run higher boost pressure on pump gas. Interesting BM has lowered it by quite a bit compreed to the B58. 

 

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Yeah... I got a bit interested in this kind of stuff when I was working with my supercharger. I was working the boost up by driving the s/c faster and faster with different pulleys, and eventually ran into what I thought was an ignition breakdown problem when I got up to 15psi on 95 octane. This was on a 1600cc engine running 8.9:1 compression..maybe 9:1 as I used a 0.8mm MLS head gasket. Eventually I realised I was running into det around peak torque as the effective compression ratio was just too high for full timing on 95 octane, even with a water/meth system.

Looking at the chart you can see why :D So I had to pull a bit of timing in the rpm range where I was having the problem. Changing to 98 octane might have helped but I was in a pretty steep learning curve at the time and didn't think of that until I tried every other possible solution. I like to think that the BM engineers are a hell of a lot smarter than me, and that they have figured dropping the compression gives the results they were looking for with the S58 engine.

Cheers...

effective CR.png

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