Time Attack Build Blog

[gixxerdrew]

This is my favorite thread to date... thanks for keeping us posted on all your progress.

Quick question: I get the advantages of having wider front wheels on your FWD car, but what is the benefit of having a smaller diameter wheel in the back (i.e. 17" vs. the 18" you're running in the front)?

Wow, thank you!

There isnt one really an advantage to 17s besides ride comfort for the street. I had four 17x8.5 wheels on the car before then I bought new wheels just for the front this gave me two extra wheels for the rear because what used to be the front is now the rear's spare wheels. Eventually I'd like to buy matching 18" rear wheels but there is no real pressing need to. It also makes tires a little cheaper. Tires are one of the largest expenses in my race budget.

On the ride comfort thing the rear suspension/tires has a much greater effect than the front on comfort I really do still street drive this car its actually pretty comfortable and nice inside. Solid motor mounts is the only thing...

 

[romeen]

Drew, are you running solid mounts x4 or just front/rear?

Also, going back to earlier in this thread, any particular reason you got rid of the EVO sodium filled exhaust valves?

Like others have said, I have been following this closely and really look forward to updates! Fantastic work. I admire the scientific approach and careful thought that you are approaching this with.

I've scrolled through your Douro Oni site quite a few times now.

 

[drivemusicnow]

So I get how you can measure downforce using suspension position vs speed, but I'm really not sure how you're going to separate a drag value out. I mean, if you assume that parasitics are linear with engine speed you could get some data off of acceleration between specific speeds in different gears on the dyno (divide out the tractive effort difference between gear ratios). That's a large assumption and you'd still be left with a lot of uncertainty, but we're just trying to get as close as possible with the tools at hand.

But it might give you a minimum loss that you could discard from your drag calculations so you could more accurately show % increase of downforce versus % increase drag.

Otherwise you could just toss up $20K for some wind tunnel testing and bribe LG and his team to help you out ;-)

 

[Flash]

Drew, this is killing me. You obviously are into data acquisition quite a bit, just splurge and get the Motec dash display to go with the Motec ECU. Just do it!

 

[gixxerdrew]

Drew, are you running solid mounts x4 or just front/rear?

Also, going back to earlier in this thread, any particular reason you got rid of the EVO sodium filled exhaust valves?

Like others have said, I have been following this closely and really look forward to updates! Fantastic work. I admire the scientific approach and careful thought that you are approaching this with.

I've scrolled through your Douro Oni site quite a few times now.

Thank you And thank you to this community for being interested and supporting us just by rooting for us, or whatever. It is appreciated!

I'm sorry I keep a lid on the specifics of my cylinder head. It's one of the few things I hold closely, but I'm sure eventually everyone will figure it out, I just hope long enough that I have come up with something new to be packing for the competition. I tried to think of a way I could answer that question without revealing too much but I couldn't. I do apologize for the secrecy.

The solid mounts are just front and rear although if I redo the sides I will likely go to solids, there is a lot to be gained there in terms of chassis rigidity by making the engine structural.

So I get how you can measure downforce using suspension position vs speed, but I'm really not sure how you're going to separate a drag value out. I mean, if you assume that parasitics are linear with engine speed you could get some data off of acceleration between specific speeds in different gears on the dyno (divide out the tractive effort difference between gear ratios). That's a large assumption and you'd still be left with a lot of uncertainty, but we're just trying to get as close as possible with the tools at hand.

I've found a very high rate of accuracy from taking the basic formulas testing and adding adustments.

The two principle forms of drag in play are aero and rolling. There are basic formulas for both. I'm not sure I understand the problem your foreseeing? There are other effects besides what the basic formulas are but they are fairly predictable if your only looking for a reasonable amount of accuracy.

 

[gixxerdrew]

Drew, this is killing me. You obviously are into data acquisition quite a bit, just splurge and get the Motec dash display to go with the Motec ECU. Just do it!

Haha yah I'm already on it but I wont be able to afford any dash until later on this season because of that but yah I did decide to just get the MoTeC SDL. After using and studying I2 this much, I went to the race tech software when we were testing some wiring and I wanted to stab myself in the face when I was using it. That was the deciding factor. I used to think the racetech stuff was awesome!

Damnit, #1 I'm going to be broke all summer now and #2 I'm officially a MoTeC nut swinger.

 

[tristinGrind]

I dont really post on this forum, I usually just lurk but this thread was way too good to pass up. Its been subscribed and Ive even passed the word onto other DSM forums Im on. Youre doing some amazing work with this project and have always wanted to see something like this come about.

Not only is this thread full of actual science and facts to learn, but its got so much heart and determination and I think thats half of why I like it so much. Keep up the good work, and good luck this season. I wish you guys the best.

 

[gixxerdrew]

Thanks mate! I'll keep busting my ass for as long as I can.

 

[romeen]

I'm sorry I keep a lid on the specifics of my cylinder head. It's one of the few things I hold closely, but I'm sure eventually everyone will figure it out, I just hope long enough that I have come up with something new to be packing for the competition. I tried to think of a way I could answer that question without revealing too much but I couldn't. I do apologize for the secrecy.

Nothing to apologize for, you never know if the competition might be reading this.

I'll just have to come up with a more Machiavellian strategy to get it out of you.

The solid mounts are just front and rear although if I redo the sides I will likely go to solids, there is a lot to be gained there in terms of chassis rigidity by making the engine structural.

I never thought of the side mounts having a significant affect on overall chassis rigidity and handling but I guess minimizing the side to side movement as well as front to back should provide better control.

Thanks.

 

[gixxerdrew]

Yah definately! theres up and downsides of it though. On F1 cars for example the engine and gearbox are very major structural components in the rear of the car.

 

[susafuss]

The solid mounts are just front and rear although if I redo the sides I will likely go to solids, there is a lot to be gained there in terms of chassis rigidity by making the engine structural.

For mounts are you using metal mounts(ie steel/aluminum mounts)? I just ask i was wondering if you have looked into maybe using solid Delrin to make your mounts. I brought this subject up with a friend of mine that was making lots of tourqe and we did some research finding out that solid metal mounts could cause to much stress on the frame causing it to break where the mount meets the frame. Delrin is a good substitute to keep the vibrations from causing this. I now have a full delrin push in mounts on my car(420a) and i love them.



Also with that being said, major props to you sir. I love project builds but the thing that amazes me the most with yours is the knowledge that you have and the very thought out way you are going at this, i am very impressed.

 

[gixxerdrew]

For mounts are you using metal mounts(ie steel/aluminum mounts)? I just ask i was wondering if you have looked into maybe using solid Delrin to make your mounts. I brought this subject up with a friend of mine that was making lots of tourqe and we did some research finding out that solid metal mounts could cause to much stress on the frame causing it to break where the mount meets the frame. Delrin is a good substitute to keep the vibrations from causing this. I now have a full delrin push in mounts on my car(420a) and i love them.

Delrin is a really neat material and if I had it to do again or do it for my supra I would go that way. For the eclipse though I was thinking about the extra vibration and load on the chassis but I really think it would be OK but my whole engine bay is going to be boxed in and reinforced anyway. Delrin would not be structural though you need to go solid metal for that. Delrin is a much weaker material than solid steel it will be the weak link.

Also with that being said, major props to you sir. I love project builds but the thing that amazes me the most with yours is the knowledge that you have and the very thought out way you are going at this, i am very impressed.

THank you so much guys these compliments are really awesome. I'm not getting cocky or anything but they really are appreciated I hope all this work pulls some wins out for us. The compliments just keep the fire going.

I have another quick update from the body shop on the side skirts every free minute I get I'm studying I2 and coordinating with people so sorry if I'm posting quickly and leaving things out.

I thought he did a really amazing job with this he said you can almost stand on that ledge.

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The material is aluminum honeycomb.

 

[vanilla gorilla]

Since I do very light bodywork, and love bodywork and paint, I love getting to see extensive body mods. Especially in process, step by step pics.

 

[gixxerdrew]

Yah! please enjoy it. I'll post them as I get them.

 

[gixxerdrew]

Another update for tonight!

you guys getting these almost as fast as I am sometimes.

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[logic]

See, the skirts are cool and all, but I want to see what the underside of the car is going to look like. I'm just assuming you're doing a full undertray, but I'm curious if you're going to be redirecting any of the air up front into the wheelhouses or running anything front to back to channel the air? And I really want to know what you have in mind for the rear wheelhouses and bumper cover. You just don't see very many people doing "real" aero work on a DSM, so this is very cool to see.

It's great to see this coming together for you. The bodywork alone would make most people think twice about tackling any of it, and I'm still jealous of the MoTeC setup. Keep the updates coming, this is all pure motivation for those of us who need to get off our keyboards and back into our garages.

 

[gixxerdrew]

I have no idea what your talking about what is an undertray?

But in all seriousness we're barely getting the outside body done in time for may race. The rest of the aero package, new diffuser, bellypan, little bit here and there wont be ready till fall events

 

[Flash]

What's the point of the ledge? I have seen them on many time attack cars. Also some cars like the Cyber Evo have a skirt on the side that pretty much hangs all the way down.

 

[snowborder714]

I'm also really interested in what you're doing with the rest of the aero package, especially when comparing the car from before and after.

You and your crew are doing an awesome job. I wish I knew (or even semi-understood) more about data acquisition. It looks like some really neat stuff that you're doing. And to be able to log all of that info would be amazing!

 

[KBR]

damn Drew, are we going to make it on this months race??


aite, peace.

 

[gixxerdrew]

To answer about the side skirt fence. Some of you will probably just look at the photos 1,2,3 and totally get it but some might need to read through the lengthy explanation (I'm still learning a ton every day too): Theres a low pressure behind a moving body in a fluid In this case the fender is protruded into the air stream. The tail end of the fender is vented so to leverage the area of low pressure on the backside of that moving body for the purpose of decreasing the pressure in the wheelhouse. When you have an area of low pressure the air from all directions that is of a higher pressure wants to fill that area. Take a look at this high speed photo from my land speed days:

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This photo was first interesting because the bumper was getting crushed and the RM lip was flexing like crazy. But take a look at whats happening aft of the front tire and in the under body. It will draw air out from the under body and it flows up into the sides of the car because its filling that low pressure wake form all directions as you can see in the photo. There there is no suction force only high pressure pushing to low pressure but people know that as "sucking" that air from under the car around the car, everywhere.

Here it is with arrows to show the flow motion.

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The third photo shows the new aerodynamic addons, I added mirrors since we did not use mirrors in land speed and their effect is important on this new aero package. Black represents new aero package addons, red represents air flow blue represents the low pressure region being created. The gurney flap helps the air coming over the fender hit the mirror and flow over it. All this is to create and maintain low pressure aft of the wheelhouse.

The wall we're building at the base of the sideskirts delays the air flowing into the low pressure area decreasing its pressure. The air from the underbody trying to flow into that low pressure has to battle with oncoming air as well so the further out it goes the more forces pushing it backward it encounters elongating and strengthening the low pressure area. it also helps with some other underbody stuff, same with the low on the fender louvers that are being created but that's the main idea behind them

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[gixxerdrew]

I'm also really interested in what you're doing with the rest of the aero package, especially when comparing the car from before and after.

You and your crew are doing an awesome job. I wish I knew (or even semi-understood) more about data acquisition. It looks like some really neat stuff that you're doing. And to be able to log all of that info would be amazing!

Thank you!

damn Drew, are we going to make it on this months race??


aite, peace.

Karlo body shop is roughly one day behind schedule but catching up. I want a shot at the title! Hope your ready to swap that suspension in and get prepped for test day!

 

[gixxerdrew]

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[wishihadatalon]

holy large Don't want all of the pressure build up in the wheel wells huh? This stuff is so cool to me.

 

[logic]

That last picture is pure sexiness. I was really hoping I'd see something like that with the widened fenders, because I don't think I've ever seen a 2g with proper louvered fenders before.

By the way, love the lip in the land-speed picture.