11 July 2016

I forgot to mention yesterday that I did some quick “hand sensor” airflow experiments about where to get air for the intercooler. There are three possible locations: each side of the main roll hoop, above the top edge of the windscreen, and above the main roll hoop.

Each side of the main roll hoop

I was unable to reach back to feel what the airflow is to the sides of the main roll hoop. I would like to retain rear visibility and some might wonder why I care. Try tipping your rear view mirror up in your commuter car and driving to work that way; it may be a little thing but can be a nuisance. Granted, side mirrors can be added to handle losing the rear view mirror, but it would be nice not to. Retaining rear visibility seems to argue for side inlets but there are two strikes against that approach. First, there’s only a couple inches above the intercooler before it intrudes into the rear line of sight. Also, just having side scoops completely block the center mirror’s view of the car’s blind spots, so going with side inlets isn’t an automatic winner. In fact, depending upon the size of the side scoops, they may even block rear visibility of the side mirrors as well. Before writing it off entirely, airflow needs to be measured.

Above the top edge of the windscreen

The airflow is strong and very smooth as expected and is the clear winner airflow-wise but means running a large duct back over my head and down to the intercooler. Visually it’ll be a big deal, but having a wide scoop along the front edge means it could be fairly low profile. I’ll have to do a mockup to see how wide it can be before it gets in the way of getting in and out. Of course, a shift in perspective is to consider it a feature – a roof. Depending upon shape, it could serve to cut down on both wind flow and perhaps even as hard points for mounting future doors. It would take the most fabrication and time though.

Directly above the main roll hoop:

Airflow was also good though about 6″ higher due to turbulence from the upstream chassis tubes and windscreen. Right below the main roll hoop the airflow was flowing forward which wasn’t surprising, but it was still impressive how airflow could be opposite just inches apart. Anyway, this is the most direct and shortest (and lightest and least labor-intensive).

Regardless where the inlet is placed, a good first step would be to use manometers to measure pressure differential. Take a length of clear tubing, staple it to a board in a U-shape, fill it slightly with water and then run each end of the tube to the test points. Those points could be both sides of the intercooler, or for an even more direct comparison, measure differential pressure between the three inlet points, looking for the highest pressure of the three.

For mock up purposes, cardboard can serve well, cut and taped to the intercooler with plastic drier ducting serving to route inlet air. It’ll look odd but I’m used to that 🙂 Or just go straight to fabrication, making it from aluminum sheet or composite.

What I don’t know is how large the inlet need to be; obviously the bigger the better but at some point it’s a case of decreasing returns. I haven’t found any equations or rules of thumb for how large the inlet should be relative to the frontal area of the intercooler.

Lastly, air to the air filter needs to be picked up from somewhere other than the engine compartment – I just haven’t gotten around to it. As it is now, at the end of the test drive yesterday, inlet air temperature was 46 degrees C (with no boost) so it needs to change. It’ll have to come from either the same ducting feeding the intercooler or a separate inlet to the top of the engine cover.

 

4 July 2016

Happy Fourth everyone.

A lot has been happening and it’s become apparent just how much I changed and how much has to be redone. Moving the turbo had all kinds of unintended (read: not thought through) consequences; every hose and tube connected to it changed. A fair amount of today was spent fabricating the seemingly simple intake elbow, but which had to be made just so in order to fit. Because I switched to a different type intake air temperature sensor, it needed a custom mount (thankfully I already measured its resistance curve). The new air sensor has a much faster response time, important in a boosted setup and is a Bosch 0 280 130 085 if you’re interested.

As you can see from the pictures the intake tract is very compact and the only real concern is how much the engine moves around due to torque. Don’t want engine movement to be able to pull a hose off, which means the fore and aft engine mounts need to be fairly stiff. I have a block of Delrin to fabricate a stiffer rear mount if necessary.

Moral of the story is that I need to quit fussing with the car and just drive it. Unfortunately there’s still the big project of fabricate the ductwork to get air to the intercooler. It’s either going to make the car even look more comical – or more bad-ass, not sure which.

While there’s still stuff to do before first start the list is getting shorter. There’s fabricating the wastegate tubing down to the exhaust, lengthening the wires for both the boost controller and the O2 sensor, finishing up the coolant bleed lines, and not much else, so it’s safe to say after checking everything for tightness, it should be running pretty soon.

Oh, almost forgot, that last picture of the wiring, notice how the green wire has backed out of the relay connector. I wonder how long it’s been that way. You find a lot of stuff isn’t as it should be when you take apart a car.

Lastly, if you want to comment on anything posted after today, click on the post’s title, which will almost always be the date, then scroll down to the bottom for the comment field.

15 May

A number of things have happened:

The forum is back online and the forum software updated; this should be the end of interruptions for a long time.

Intercooler placement was finalized (read: “make a decision and move on”), placing it on the centerline of the car. In a straight-on rear-end accident, if it gets pushed forward it’ll hit the main roll hoop diaganal, and if it somehow gets past that, it should pass between the seats. With that out of the way, the end tanks were finished and welded on; in 15 years, this is only the third time the cooling fan has come on – welding thicker aluminum requires significant current. As to how much air can be fed through it, I’ll be learning along with you guys. An F1-style scoop would certainly work but will block rear visibility. Another approach is having scoops protruding from each side feeding air in that way. All will become clear after some aero testing.

It’s official, the cylinder head and various engine parts were delivered to the engine builder, Jeremy of Drag Cartel; we met midway at an import car show. I only took a few pictures because it irks me that so many people do the “I’m different – just like all my friends” thing, a lot of chrome, a lot of turbos, and not much independent thinking, including a surprising lack of air filter elements. Independent thought was noted, such as an old Honda 600 with a Honda bike engine (and gas tank) that fit like a glove. Jeremy’s drag car was a work of art, very elegant; it was clear that someone knew what they were doing. That engine generates around 400 hp at 10,000 rpm. I noticed that the car used the same remote oil filter adaptor I am – the one where the nut backed off, leaving me stranded with oil everywhere. I let him know. I got there really early to hand off the parts to Jeremy before the crowds arrived, and arrive it did. I left about 10am and there were 100s of Hondas backed up out to the freeway heading toward the event. The police took notice as well, with several cars pulled over at any one time. Get a bunch of young roosters together and there’s always one that has to show off, and presto, red lights. Need to learn to contain it, guys.

Lastly, work on the new website continues. Right now I’m trying to figure out how to use the blog page for this year’s blog, but somehow have an archive directory to previous years.

17 April

The re-designed intercooler placement takes shape. New end tanks have to be made, both because there’s not enough space for the previous ones, and as my buddy Alan reminded me, with around 20 psi boost pressure, that ends up being hundreds of pounds of force. Given a chance, that force would flex any flat-sided tank, work-harden the welds and cause them to crack; the new tanks will be cylindrical to avoid that. After taking these pictures, I changed the tube routing on the inlet side. As shown, the flow would have had to take a very tight 90-degree turn right out of the compressor, which is terrible for flow. The turbo outlet will be rotated to point downward and the flow will instead be fed through two large-radius 90-degree bends feeding into the center of the end tank from below. It’s also cheaper because the U-bends are already on-hand.

What will be decided later is where to get the cooling air from. Which approach to take will be determined with some test drives, string on sticks to determine flow direction, and clear U-shaped water-filled tubes serving as manometers to determine relative pressure. Regardless where it comes from it sure is going to change the appearance of the car – so be it.

The new engine is slowly coming together; shown is a coated piston. This week, the pistons, pins, and rods will be sent to ERL where the block will be honed and the short assembly clearanced and balanced. After that it’s back to the engine builder to add the inspected cylinder head and then we’ll be back in business. Reminds me that I need to send the head and various parts to the engine builder pretty soon so that I’m not holding up anything.

In other news, as seen from above, the driver’s right-hand shoulder belt bracket was found misaligned but wasn’t loose – I didn’t set it that way. Seems the spin at Willow may have been more forceful than I thought and with the car spinning to the right and catching the dirt bank, I apparently tried to keep going toward the left. It’s crossed my mind a few times that the HANS may well have prevented some serious neck injury.