RebekahsZ Posted June 7, 2015 Author Share Posted June 7, 2015 (edited) Finally: on the sealed airdam (fenders still provide access to cold air) vs a small hole cut in it. I ran 167 today in both configurations. However: with an engine water temp of 196 at the starting line, the opened airdam had a temp of 199 at the finish line vs a 230 water temp at the finish line for the sealed configuration. I don't really know how hot is too hot. Stop the car and turn off engine and temp went to 207 for open dam and 244 for closed. The way to cool this sucker is to pull the hood and leave it running with the fans on. So yeah, it matters for temp - didn't matter for speed. I think that's the basics of my trip report. I left with some questions answered, but lots more questions to work out. I still have issues beyond "more power" to work out before I worry about going faster. But a months work with fiberglass (time to start cleaning shop) raised the Lomax Racing ECTA C/GMS record of 161.3 to 167.5 last month then further raising it to 174.2 mph (I will admit to a little tail wind yesterday). Not bad for a tired old Z car built and worked on by a guy who really doesn't know what he's doing. Glad to have all the hybridz help. Edited June 7, 2015 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
tube80z Posted June 7, 2015 Share Posted June 7, 2015 For the springs I'd run the rear either the same or perhaps 50 pounds lower in rate than the front. The higher rate will help keeping the chassis from moving so much and if the suspension is compressing from downforce it will about half of what you're seeing now. I'd agree on as much caster as you can do, which will also increase the wheelbase and help with stability. In looking at the picture of your car from the side it looks like you need to lower the rear. That would reduce the angle of the windshield and might get you a few more tenths. Any reason no rear spoiler? That should help reduce drag and make the car more stable at the speeds you're running. A friend has an EP car and it routinely hits 158 on the straight at PIR and when braking the car is moving a lot from the in car footage. He said when he ran the GT-2 Z it was much better in this regard. One difference was the rear spoiler. Hope this helps, Cary Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted June 7, 2015 Author Share Posted June 7, 2015 (edited) I was hoping to do rear spoiler testing next year in May meet. I have a small BRE style spoiler and I hope to buy a Victory spoiler as suggested. I had to get clarification on spoiler/wing rules and I got the clarification I needed. Burton Brown runs in a very restrictive Production Class so he restricted to OEM chassis parts. I'm competing in a Modified Class which is much more permissive. Wings are forbidden but any spoiler is allowed as well as vortex generators. I will work this winter on getting the bolts of each spoiler to line up. From what I've seen, the mounting of the Victory spoiler is kinda chicken shit with just like 4 bolts/scres down the middle. I'm suspicious of that being inadequate, so I will need to doctor it some. I need to reference the existing wind tunnel data to better understand the spoiler situation, but I will do that in the weeks ahead. I sure thought a spoiler would cause a lot more drag..??? Perhaps not.. I'm new to this but I'm eager to learn. Since the front of the car kissed the pavement with and without the splitter, I will be making splitters of varied length that I can attach quickly and TnT. One thing I can't get my head around is how down force affects straight line car behavior. I inderstand why you desire it going around a road course. The negative behavior I experienced was a general twiitchiness and drifting in the lane that started above 100 and got more noticeable with increasing speed, then an uninitiated steering of the car under braking. Toe-in seems to have fixed the steering under braking. I guess I don't really know what car behavior is included in discussions of "stability." And I don't know what levels on perfection and comfort are to be accepted and what degree of pucker factor is just par for the course. While we made big improvements in how the car drove while braking, I don't feel that we really gained anything duri g the accelleration portion of each run. Edited June 8, 2015 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 7, 2015 Share Posted June 7, 2015 Spoiler reduces drag on a Z, unless it's huge. Competition Car Aerodynamics by McBeath and Race Car Aerodynamics by Katz will help. I know McBeath specifically shows why, and also is where I pulled the quote about splitter adding next to no drag. Good book, and he also does the wind tunnel testing that you see in Racecar Engineering magazine. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted June 8, 2015 Author Share Posted June 8, 2015 (edited) Jon, how big is "huge?" That just doesn't sound right.....oh, and I dropped the ass of the car an inch after the first splitter scraping event and kept it down. Observers say it looked a lot more flat. The static rake was intentional but perhaps excessive with an additional 3" of nose down with downforce on the splitter. I tried to video the rear wheel with the flare removed to try to see how i was doing in both travel and clearance. but the camera kept blowing off target. Will see this week if any of that video is beneficial. Next year, I'm hoping forum member Spitznaugle will come again and video the car at the fast end of the track. He was a big help with cutting off the splitter and repairing it, then we had supper together after the pits closed. I had a great pit crew. Edited June 8, 2015 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
jt1 Posted June 8, 2015 Share Posted June 8, 2015 I agree with the others that a spoiler will tighten the car and not hurt the top end a lot. A lot of the drag force is applied to the front of the car, ahead of the centers. All the force pushing the car forward is applied rear of the centers. So when the car yaws a bit, the drag force goes to one side of the centers. The front of the car is pretty well stuck, so now the rear moves more than before. And the car is spooky loose. Some of us around here have seen the same thing on the road courses with fast straights. Look thru the rear spoiler data in the WT tests. If it's legal, a whaletail might be your best option. Congrats on having a successful trip!!!!! john Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 8, 2015 Share Posted June 8, 2015 If you read through some old posts, you'll find Coffey's spoiler which was built off of a Car and Driver magazine article. I can't remember the size, maybe 6" or 7" and the angle was 30 degrees IIRC, and this was supposed to REDUCE drag and I believe it eliminated lift but didn't provide any actual downforce. As John says, the windtunnel testing proved that the whale tail made a lot of downforce and it also didn't have a lot of drag. . Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted June 8, 2015 Share Posted June 8, 2015 (edited) This one? Edited June 8, 2015 by rturbo 930 Quote Link to comment Share on other sites More sharing options...
jt1 Posted June 8, 2015 Share Posted June 8, 2015 That's similiar to the one Jon referenced. I remember that discussion, pretty sure it was 7" and 30 deg. The whaletail I'm referring to is the one like a 930 tea tray, maybe from the IMSA cars? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 8, 2015 Share Posted June 8, 2015 Yep, that's Coffey's. The whaletail made a lot of downforce in the windtunnel and the drag was modest IIRC. That would probably be a good place to start to match up to the splitter. For the airdam alone, I'd look at John's spoiler. Quote Link to comment Share on other sites More sharing options...
socorob Posted June 8, 2015 Share Posted June 8, 2015 175 mph in a Z must feel like 200! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.