[farmergiles]

What sort of losses are we talking about here? like if it was in the boot for example.

duty cycle ive no idea what that is. I know what it means though I have that on my welders. How would i find out? Idont think its going to be easy to get data sheets

that battery looks a reasonable size any idea on dimensions? might be possible to put it in the engine bay but is 8AH going to be enough? its a 7kw system on the Audi just for the turbo itself.

charging havent got to that yet but there are plenty of options such as running a second alternator. i believe the original charges from the alternator on the car

You will get a couple of minutes max from an 8Ah battery so realistically, enough for a few 'boosts'.
How are you going to recharge the battery? You'd need a DC-DC converter and electronics to control it.

Also, a sudden surge in torque will probably unstick the rear tyres causing possible loss of control.

To be honest you'd get a better result from remap and new maf. You'll need to up the fuel anyway otherwise all that will happen with the extra air, is a big flat spot and serious juddering.

Don't expect a nice smooth transition from the 'boost' to the main turbo either.

What are you actually trying to achieve? Do you feel your 320d is flat at low rpm? if so, change the maf.

Honestly this is the most mad idea I have ever heard of as a diesel tuning mod.

What do you think the clutch and gearbox will think of the sudden boost in torque?

 

[farmergiles]

Not an expert but i always believed Turbo's worked on exhaust gases via exhaust manifold (get exhaust gases out quicker, maker more power) , and Superchargers worked on getting air into the car engine quicker by pushing it into the intake manifold, to make more power.

I have know of several specialist cars over the years that were both Supercharged and Turbocharged at the same time.

Wrong. Both work by forcing more air in. The turbo is driven by waste energy in the exhaust and the supercharger is driven by the engine.
The supercharger can work from lower rpm and doesn't tend to produce the unavoidable lag that turbo's suffer from.

Because the turbo relies on waste energy, the engine has to be producing some - it's a chicken and egg situation, before it will speed up and produce boost, hence the lag. A turbo actually impedes exhaust flow, which is another reason why doubling the pressure does not give double the bhp.

It's quite easy to envisage what happens with forced induction. Without it, the 1bar of atmospheric pressure is all there is to push air in, add 1bar of boost, then in thoery you can double the airflow and so on. Of course in practice there are losses so doubling the boost doesn't double the power, even if there was enough fuel being injected.

 

[farmergiles]

Don't listen to the nay-sayers on this. I did something similar using a built up electric powered Garrett turbo for Escort Cosworths. It worked in a crude way but was much heavier and complex than anti-lag that was developed at the same time and didn't require homologation.

The op has no electronics knowledge if he doesn't know what duty cycle is and hasn't said how he plans to recharge the battery.
Unless he has someone lined who does have the relevant knowledge and skills he has a lot of issues to overcome.
He's also not said how he will plumb in the electric turbo and how he will control the changeover valve.

 

[farmergiles]

i didnt say i didnt know what duty cycle means, i just dont know the duty cycle of this turbocharger.


plumbing in etc is not something im concerned about right now, what im concerned about right now is doing a lot of research getting some opinions from others and then deciding what the next thing to buy will be. for wiring and electronics thats my brothers department he is a tuner, engine builder and he works with aftermarket ecu's etc.

Fair enough. You obviously like a challenge!

 

[farmergiles]

So ive been doing a bit of research ive found some places do 1000w 48v alternators is that enough? i also found out that many cars with 48v systems use a dc to dc converter for charging but i didnt find any info on the alternators themselves but i expect they are probably 48v alternators which are used to charge both the 48v battery and the 12v.

also i foumnd an original audi battery and here isa picture from the sticker so we can see what its specification is. battery doesnt look tall but i would like to know how long and wide it is

You still must have a BMS (battery management system) to control charging and be matched to the type of batttery chemistry and battery spec. You must NEVER allow an overcharge to happen to a Li-ion battery because it will go into meltdown (catch fire)

A DC-DC converter will be needed to charge the 12v battery AND supply all the 12v electrics, if the only alternator is the 48v one.

(a 12v alternator rated at 70amps is 1000watts, so 1000watt 48v one should be about the same size, but only rated at 20amps, so the DC-DC converter will need to provide 12v (14v) at potentially 30amps or more for all the 12v electrics)

So in a nutshell, you will need:
1) 48v battery
2) 48v alternator
3) BMS matched to the battery
4) DC-DC converter with charging controller
5) PWM controller for the turbo
6) Interface between the engine ecu and turbo controller.

 

[farmergiles]

yeah, i dont really get the premise tbh. The stock engine has a variable vane turbo and hits full boost extremely quickly already. Sure, it doesnt make much below 1500rpm, but why are you ever trying to request full power that far down the rev range? Select the correct gear and your at 2500-3000rpm and response is instant. Its also modifying something where the solution already exists, and in the case of the E90 that solution is the 330d, or 335d for even more go.

One thing the bigger engine does, is makes the lower RPM range more flexible, simply by virtue of 50% more capacity and thus 50% more power even without any boost. If you do find yourself in the wrong gear it doesnt matter as much.

Maybe its just an age thing. I remember when i was younger, modifying cars, and always wanting to "do something different".... I did daft engine swaps that looking back now i can see made zero sense. My brother had a 320d, and we did various bits to it including injector upgrades and larger turbo etc. Most folks on the BMW forum pointed out we should have just bought a 330d. Somehow we thought we knew better... Some time later i bought myself a 330d, and immediately realised that indeed they were right. It was just better in every possible way. Not only did it make more power in a much nicer way, it had a wider power band, it was smoother, it sounded nicer etc etc. A completely stock 330d was better than that tuned 320d ever could be, and ofcourse, the 330d could easily be remapped for even more. He eventually stripped the 320d for parts because he couldnt sell it for what it was "worth" and having learned theres no replacement for displacement, bought a 130i.

Eventually i realised the common approach that i rubbished when i was younger was common because it worked and people had gotten to that point by iterating thru the other options and finding the best one.

Given how difficult its been for OEM's to get electrical turbocharging working and viable (they've been working on it for at least 20 years) I think the idea that your going to bolt such a system to an existing engine, and somehow have it work properly, is just nuts. Especially when the intention is only to provide a tiny bit of boost below 1500rpm, where you basically never should be anyway... Maybe you find the process of building the thing fun, but again, with time i've realised that jumping into something that Just Works has its benefits. If the thing you want doesnt exist, then sure, build it. But in this case, you could either fit the larger engine, or if for some strange reason you want to keep the nasty 4 cylinder, grab the twin turbo arrangement from the 123d, and get that working on your E90. At least someone with millions of pounds has engineered a solution that does actually work, and you just have to tackle the challenges of making it work with your particular car.

You can adjust the vane linkage so the vnt makes more boost a low rpm, and with a decent remap you can hit max boost well below 2000rpm. If the remapper knows his stuff, he can also raise the boost pressure and alter the map calibration so the ecu is happy with the new boost profile.

If the performance below 2000rpm is very poor, the maf needs changing. (or the remapper can eliminate it).

The BMW 2L in the 75/ZT could be remapped to 160bhp from 113 and that engine didn't have a VNT turbo. The same engine in the Freelander TD4 which does have a vnt has reached 178bhp.
In both of those cases, I'd worry about the drive train longevity.

 

[farmergiles]

330e PHEV?
How will you insure it? Adrian Flux might consider it.

 

[farmergiles]

correct to a point you can adjust the linkage if its a vac operated turbo it has to be done on the map if its electronic. mine is electronic so its a faster response compared to a vac operated one there are tradeoffs for this sort fo thing so it depends on the individual and if they are prepared to accept them.

once the car starts spooling about 1500 rpm on mine it will spool up and rev very quickly i have a hybrid turbo as well, also it doesnt have a maf that has been mapped out it runs what it needs to off the map sensor. in any case a maf sensor has its limitations so while its useful its only upto a certain point.


many 2.0 turbo diesel bmws often badged for example 116 118 316 318 those are the same engine as the 120 320 520 variants in many cases the difference is a detuned ecu and they also run different turbo and injectors. so if you were to upgrade those to 320d versions or even better those will tune exactly like the X20 variants. my brother bought a 118dfor his project and the reasonthats a good choice even for people who want to just tune that engine is theyve had an easier life with less power.

Not all 2L engines are the same. The cheap ones (<150bhp) don't have balancer shaft nor intake flaps) these ones were sold to Rover for the 75/ZT/Freelander TD4 and possible in the very low power BMW/Minis (122/136bhp). They are a slightly different capacity. (1950 v 1998cc I think)

 

[farmergiles]

I've dabbled with can bus vnt actuators but was able to find the data I needed online for Holset & Hella turbos.

Otherwise you need to sniff the data on a vehicle with an e-turbo. Even then it won't be quick and simple to decipher which frames and bits do what.

If the turbo is sending dtcs, you should be able to filter them out, but also find out how to reset it - it would probably have gone into a fault state if dtcs were generated.

This happened on the Holset actuator if the actuator was not fitted to the turbo. It took me a while to realise what was happening then the penny dropped. The actuator moves the vnt mechanism from end to end so it knows where these are and when not fitted, the actuator lever was moving too far.

 

[farmergiles]

yeah thats the thing it may go into a fault state if DTC's are generated like you say so that is a bit of a problem

i know on hella/Garrett actuators they do a self-test going end to end when you turn the ignition on I expect its the same for other turbo's

The end to end thing also scrapes soot from the vnt mechanism. Holset actuators can be sent a command to do the same and also move to the exhaust brake position. They require power cycle to reset them out of a fault mode.