[ArvidW]

@MileHighScottie, What system did you use on your volvo? Could you give some details about the parts used, the difficulty of the tuning?

If i remove the IC there is place available for a small pump and reservoir. So it may be a viable option...

Some plots of the MAP (just before throttle bodies), eMAP (exhaust manifold before turbo), CAP (just after compressor wheel):

The pressure drop over Intercooler + piping:

The ratio between exhaust manifold pressure and the pressure at compressor wheel (Absolute and Relative measurement, don't know whats commonly used):

 

[MileHighScottie]

I used an Aquamist system, which i tapped directly into a charge tube just before the intercooler. It is essentially a small injector and trips from manifold pressure at whatever psi you specify. I was running 29psi (1.95bar) with a large Garrett into a 2.4L 5cyl, so not really the same but it may be worth looking into.

Here is a link to one application: http://streetfighterperformance.com/xb12-turbo/turbo/water-injection

Sent from my SM-G950U using Tapatalk

 

[ArvidW]

10000km later and the 955i engine is still going strong. The bike has run great without major issues at 0.65bar boost.

I've bought a replacement for the Smart Fortwo intercooler. The core will be used to build a new single-pass intercooler with custom end tanks that should have a significantly lower pressuredrop. This should drop the load on the compressor and therefore lower turbine backpressure. I hope to get a bit better cylinder scavenging, lower combustion temperatures and lower tendency to knock.

Furthermore i'm trying to improve low speed drivability. Since I've fitted the Bosch EV14 550cc injectors (original 285cc) the engine has not run perfectly smooth at low speed. I'd selected the injector to have the correct narrow twin-beam spray pattern to spray towards the two intake valves. This should limit the amount of fuel sticking to the intake channel walls. The spray is offset 9.5degrees from vertical to prevent hitting the bottom of the intake runner. Unfortunately I've ordered the wrong one, and it is now pointing at the bottom of the intake runner.

Some of the fuel is hitting this little edge, and forming a small puddle. I'll turn the injector 180degree to fix the issue, some modification of the connector is required. Futhermore i've portmatched the throttle bodies to get rid of the ridge.

The throttle bodies were also given a chamfer on the intake side as they are now connected to the intake with a silicone hose that has a larger internal diameter than the stock velocity stacks.

The last item i'm planning to modify is the cam timing. The 1st gen 955i engine is running a lot of overlap (50dg) which is not optimal with the high turbine backpressure. Newer speed tripples run less overlap and wider lobe seperation angle. I'm considering adjusting my current cams to newer timings, but am not sure how far I can go before screwing over the engine characteristics. A first idea is given below. Can anyone give me some advise suitable for the turbo bike? Goal is to improve volumetric efficiency of the engine, prevent internal EGR and improve turbo spool.

 

[ArvidW]

Short update. I converted my manual mill to CNC and machined a bracket to hold the IC:

Worked on the inlet side of the intercooler. Two identical pieces will be welded together.

The end tank on the outlet side has been machined from billet as well. Including reliefs for bolts and the radiator.

Internally I've added an air guidance feature, in the hope to improve flow distribution in the intercooler:

Pipes need to be re-routed. But will follow a more straight path for lower pressure drop.

 

[sussurf]

You're a genius

 

[ArvidW]

Intercooler is all welded up:

Not the most esthetically pleasing welds, but thankfully free of leaks.

On the bike it looks quite clean.But i'm not loving it as much as the Smart Intercooler. It's a bit bright.. Maybe coat it black?

Old setup with Smart IC:

 

[ArvidW]

The first drive with the new IC was a succes:

• Exhaust backpressure reduced from 1.5 to [email protected] & 0.65barG boost
• Injector fuel flow increased 12% to maintain the same Lambda [email protected] (AFR11.8)
• Intake air temperature is similar, or a bit higher than before
• Boost builds quicker than before (0.3s from 0 to 0.5bar boost @7500rpm)

Bike feels faster, which makes sense if it is burning 12% more fuel. Compared to the 140whp dyno run fuel flow is 15% higher, so it's probably much closer to the 158whp goal i've set years ago

The exhaust backpressure-to-boost ratio is still high at 2:1. This can lead to exhaust gas reversion (exhaust gas being forced into the intake during valve overlap). The overlap on this bike is quite high at 50dg, so i'll try advancing the exhaust cam, and retarding the intake to reduce the overlap.

I'll also focus on the K&N airfilter, it looks a bit small for the power goal... With the new IC there is space for a bigger one!

 

[sussurf]

Cool!

 

[ArvidW]

A common question I get is: "Does your bike have turbo lag". The simple answer is: Yes. But how much?

I decided to test it on the highway. From a cruising speed of 100kph (60mph) I went to wide open throttle and measured the time it took to reach 0.5bar boost. I did that in 6th, 5th, 4th and 3rd gear. Later on a B-road I added a couple of setpoints from around 50kph in 6th gear to get the response on really low engine speed.

When you plot all these setpoints you get the graph shown below:

The "turbo lag" really depends on the engine speed. At 5800rpm is it only 0.5seconds, but at 3500rpm is is more than 1.2sec. This is the response from 100kph cruising speed. If I did this again from 200kph the response would be a lot quicker because there is more exhaustgas to start with.

The lag is really noticeable when riding with friends. A speed triple (106hp?) can keep up for the first second. Once the boost hits, the heavy Sprint RS leaves the triple in the dust (only in a straight line of course). In the twisties the turbo is a bit of a drawback: Bike is heavy, throttle response is non-linear.

I still like it a lot. The turbo adds character to the bike

 

[sussurf]

Whats not to like?!!
Oh yeah, corners.....

 

[RampantParanoia]

The turbo adds character to the bike

Character, and you can rest easy knowing it's all your own work and none of your mates get that turbo spool sound

 

[ArvidW]

@sussurf, I bet a 125+whp 1050 is a better choice for circuit riding

@RampantParanoia, Exactly! You take a certain amount in pride in riding a home build, "parts-bin special", especially if it appears to be reliable