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MarkyMark77
MarkyMark77 New Reader
12/17/18 5:05 a.m.

In reply to Robbie :

Hi Robbie - if weight is a major concern and it sounds like it is, then I have some suggestions -

1. Use the bonnet as a mold and recreate it out of something cheap and light eg hemp fibre (as in the Lotus Elise).

2. Ditch the engine deck and bootlid - recreate them out of 10-mesh and flat ally.

3. Ditch the headlamp pods, OE front lights, headlamp motors & mechanisms.

4. Budget for some modern 13" wheels with good inherent balance and run a 185 on a 6J (front) and a 225 on a 7J (rear) - if you go for a custom build and calculate your offsets correctly then you can roll your rear arches and leave the outside looking stock - ie save lots of money by not flaring the arches or adding a bodykit.

5. Don't reduce the SHC of the brake rotors any - if you overcook them they'll warp and that's more time and money gone, plus factor in what's likely to happen if you need to stop in an emergency.

I can look into the oil recovery system I mentioned. Maybe your baffled sump is good enough but unless it's tried and tested, I wouldn't risk the consequences of running the big-ends dry. Autocrossing is notorious for creating rapid and opposing lateral g's.

I'm going on a road trip in the new year to have a look at a stalled replica Dallara build, as a potential donor car. It could well be ideal - it started out as a standard spec X but now has a spaceframed front and rear and a full rollcage triangulating all the suspension hookups, built to BSRCC Historic Saloons spec. It also has a 1-piece front end from grp on quick-release clips, a turbo'd 1400 motor and gearbox, and all the molds for the bodykit. The price is $5,300.

I'll post some pics of this car in the New Year.

Have fun in the meantime lol

Robbie
Robbie UltimaDork
12/23/18 5:11 p.m.

Updates!

I went to Detroit Friday to get the final parts from the parts car so Ian can get it out of his garage before real winter hits. We took the floors and the rear bulkhead panel, and I just grabbed the taillights and door handles quickly since they might be worth a little.

Started here:

This part of the floor had already been replaced on the parts car (haha!) And since they were done a bit - ahem - unconventionally, they were easy to get out. Seriously the driver side one was held in with 2 rivets and the passenger side one was held in with about triple that.

But at least that means the replacement panels haven't had time to get too rusty yet!

Next we attacked the center console. The one in the race car had been flattened in the really sketchy center seating conversion. Since I think having two seats is best (what good is an awesome car if you can't share it?) Having this console with a mount for the shifter and gas pedal and good structure for the dash would be useful.

Finally we snagged the main floors too. These do need replacing on the race car, so factory panels will be nice.

Robbie
Robbie UltimaDork
12/23/18 5:15 p.m.

Got the parts home, and they do fit quite nicely!

 

Robbie
Robbie UltimaDork
12/23/18 5:22 p.m.

Today was back to bracketology:

You may remember I started some brackets on page 8. These will hold the diff to the engine mount bar.

Next I measured and drilled a hole.

Made sure the hole was the right size for the bolts I plan to use.

Next I fit them back in the vice to make them a bit more finished looking (ie cut the edges with a sawzall):

Finally, clean up on a bench grinder, and I am left with 4 brackets that are functionally equivalent! 

 

 

Robbie
Robbie UltimaDork
3/3/19 10:57 p.m.

More brackets today. Roll the cad jokes:

Neat trick, hold the cad template up and tap gently many times with a hammer. That will trace any edges or holes perfectly.

Template = good. Onto metal. Oh, and let's add some gusset (just cut it out of angle iron)!

Drill some holes and toss in some all thread for now. Will find an appropriate length m10 * 1.25 bolt when I can.

And the back, when welded these gussets should add some extra strength.

AWSX1686
AWSX1686 SuperDork
3/4/19 8:09 a.m.

Yay! Progress! This is one build I am very much looking forward to seeing at the challenge. 

Robbie
Robbie UltimaDork
3/4/19 8:26 a.m.
AWSX1686 said:

Yay! Progress! This is one build I am very much looking forward to seeing at the challenge. 

I'm hoping that "slow and steady wins the race" comes true.

Robbie
Robbie UltimaDork
3/4/19 9:57 a.m.

I also mocked up the other 4 brackets I made perviously.

And I found that titanium headers are not in fact impenetrable fortresses. If I heat them with my torch I can get them to glow and the I can dent them with a hammer. They dissipate the heat like crazy however so I couldn't keep one primary hot while heating the others in order to bend the header like I wanted. Here it almost fits however, just a little more massaging needed!

Some other pics. Patrick provided the turnbuckles you see here. And if you are thinking "those look like Wartburg tie rods" then you would be right! I've got my finger where the drive sprocket is and the rest of the geometry is about where I want it.

MulletTruck
MulletTruck HalfDork
3/4/19 12:13 p.m.

I probably have that rear engine mounting bolt in my pile of GSXR parts. I will get to my storage unit this week and have a look. 

Robbie
Robbie UltimaDork
3/4/19 12:55 p.m.
MulletTruck said:

I probably have that rear engine mounting bolt in my pile of GSXR parts. I will get to my storage unit this week and have a look. 

Thanks! I have what I think was the engine mounting bolt, but it is too long by about 2 inches. Like maybe the frame mounting lugs are an inch or so wide each. If you find it will you measure the length please?

MulletTruck
MulletTruck HalfDork
3/4/19 1:28 p.m.

In reply to Robbie :

I ran into that on the last busa/car swap I did too. I just cut and threaded the bolt I had. I will see what I have.

Robbie
Robbie UltimaDork
3/6/19 10:13 a.m.

Started mocking up intake and exhaust. I found that the gsxr and the Fiat use the same size exhaust pipe. Hilarious.

I also found I'm gonna have to cut the bulkhead to fit the air box. No real biggie, but I'm going to try to do it nicely (which is hard for me).

So I'll need a cutout like this:

I don't love cutting this out, but I can always reinforce later if needed. Also, I don't particularly want to reengineer my own air box.

rdcyclist
rdcyclist Reader
3/6/19 12:03 p.m.

Can you reverse the airbox? On my old GSXR750 engine I believe the AB is reversible with some fabrication. The inlets are then on the "wrong" side for Ram effect but I don't think you're going to be going fast enough for that...

TED_fiestaHP
TED_fiestaHP Reader
3/6/19 12:23 p.m.

Is that the bulkhead to the rear trunk?

 Mine had a removable panel, but I needed a bigger, different hole, I added some square tubing around the hole.

Robbie
Robbie UltimaDork
3/6/19 12:28 p.m.

In reply to rdcyclist :

hmmm, good call. maybe. I'll try it. I've been having a bit of a debate about gas tank location, and reversing the airbox would mean the gas tank would have to move from the 'stock bike' location. But since the 'stock bike' gas tank location is up behind our heads in a car, we may not be thrilled to put the gas tank there anyway. 

So if we are already moving the gas tank (which I think is likely), then reversing the airbox probably doesn't take space from anything else. 

Speaking of Ram air - anyone know how the math works? for example, if the ram air vents on the front of the bike are say 36 square inches of area and they start making real positive pressure at say 125 mph, what if I made vents that are 72 square inches - would the speed where real positive pressure is created change? I have much more real estate than a bike does...

Robbie
Robbie UltimaDork
3/6/19 12:31 p.m.

In reply to TED_fiestaHP :

its the bulkhead between passenger compartment and engine compartment. "rear parcel shelf" I guess. haha. 

stafford1500
stafford1500 HalfDork
3/6/19 12:39 p.m.

Ram air is pretty simple. The effect you are looking for is to make a stagnation point at the intake face. YOu will not get much more than atmospheric pressure so there is no significant supercharging, only reducing the losses due to the pumping (suction) of the inlet. There is a possibility of a VERY SMALL supercharge effect, but that is more an effect of the volume of the car/bike/whatever moving thru the air and having to increase the local speed of the air above the vehicles road speed. For reference it is common to get less than 1/2psi above atmospheric on a cowl intake at the base of a windshield on a full bodies car.

Think of it this way: there is 14.7psi of air pressure when you are standing still. That is the total and static pressure, with dynamic pressure being zero because there is no speed. As you speed up the static pressure is reduced at the same rate that the dynamic pressure is increased AND they still sum up to total pressure. The only way to get more than atmospheric total pressure is with a mechanical pump (like a turbo/supercharger). The volume of a car does a very small amount of that, but again it is very small.

If you can get an inlet at a location that effective stalls all the air hitting the inlet, then you are getting maximum pressure (total pressure) because you have reduced the dynamic pressure and increased the static pressure, but still they must sum up to total atmospheric pressure.

That all changes when you get closer to the speed of sound, due to air being compressible, but if you are at less than ~350mph the effect can be neglected...

stafford1500
stafford1500 HalfDork
3/6/19 12:46 p.m.

Also the inlet pressure is going to be a function of engine consumption (engine speed) and vehicle speed. If the engine is sitting still and the engine is at max revs there will be a suction (low pressure) at the inlet. This can be overcome by making the inlet large enough to effectively capture enough air at speed to overcome the suction. In your example, the inlet area will need to be matched based on the flow speed and area of the inlet compared to the vehicle speed and the "Capture" area. If the flow speed at the 36sqin inlet is 100mph, you will need to have 72sqin of inlet at 50mph vehicle speed (assuming you can get a stagnation pressure at the inlet).

TVR Scott
TVR Scott HalfDork
3/6/19 1:02 p.m.

I like what you're doing here.  Fun!

Robbie
Robbie UltimaDork
3/6/19 2:12 p.m.

In reply to stafford1500 :

The stock GSXR has correction built into the ecu for the ram air effect (I guess it uses MAP in the airbox). I just think it would be cool to use the feature, but I'm doubtful this car will ever see the 150-176 mph pull that the GSXR ram air was built for. 

I understand how at less than say 150 mph i am unlikely to develop any positive pressure in the airbox. But i think you are saying there is an opportunity to reduce the vacuum in the airbox at full throttle by increasing the size of the air intake (and pointing it forward)?

Robbie
Robbie UltimaDork
3/6/19 2:12 p.m.
TVR Scott said:

I like what you're doing here.  Fun!

thanks - im having fun!

stafford1500
stafford1500 HalfDork
3/6/19 2:28 p.m.
Robbie said:

In reply to stafford1500 :

The stock GSXR has correction built into the ecu for the ram air effect (I guess it uses MAP in the airbox). I just think it would be cool to use the feature, but I'm doubtful this car will ever see the 150-176 mph pull that the GSXR ram air was built for. 

I understand how at less than say 150 mph i am unlikely to develop any positive pressure in the airbox. But i think you are saying there is an opportunity to reduce the vacuum in the airbox at full throttle by increasing the size of the air intake (and pointing it forward)?

Short answer, yes.

Robbie
Robbie UltimaDork
3/7/19 8:56 a.m.
rdcyclist said:

Can you reverse the airbox? On my old GSXR750 engine I believe the AB is reversible with some fabrication. The inlets are then on the "wrong" side for Ram effect but I don't think you're going to be going fast enough for that...

So, it turns out I think this is possible. But it would also require flipping the throttle bodies since the injectors and fuel lines will only fit on one side of the airbox. 

I'm not sure whether I like that solution however, as I would like to keep the drivetrain as stock as possible so that there are the fewest unforseen issues. for example, if I flip the TBs, then the injectors spray down instead of up. Does this matter? I'm not sure, but I do know that the up configuration was rigorously tested and engineered by smart people and the down was not. 

Stampie
Stampie PowerDork
3/7/19 11:10 a.m.

In reply to Robbie :

Smart people designed the Titanic also.

Dusterbd13-michael
Dusterbd13-michael MegaDork
3/7/19 11:17 a.m.

And amateurs proved you can fly.

Dont be afraid to berkeley E36 M3 up, and the skys tje limit!

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