no ac after 140mph???

[PoorManQ45]

My offer stands.

Ok, i'll take pictures or make a video while I go for it.

p.s. I'd rather see a picture of the underside of a valve cover / top of the head.

You want me to take my valve covers off? Is there anything to be gained by cleaning the top of the heads? If so, I might have to do it. Now you got me thinking again. I usually work on pushrod engines. So forgive my question if it's stupid.

Does the VH45DE use rocker arms? If so, what ratio are they?

[rsiwicki]

I can't get over all the controversy about the top end speed of the Q. All I know is that my car shifts exactly at 135mph from the 3-4 shift and having taking it up to mid 140's I am thinking that about 155mph is tops (maybe 160 but at 6,900rpms) on the car given all the wind resistance exponential factors involved. I would not want to put that kind of stress on my engine running at 6,500+ rpms under that kind of load at those speeds as my engine would probably go to the crapper.

[psychic_mechanic]

Maybe he's got a JDM speedo that's reading in km/h?

I saw one from canada for my old 1970 Mustang that read to 220 at a swap meet, I should have bought it to impress the ladies.

Air piles up under the hood at speed, imagine a snow plow to help with the visual. Depending on the car at speeds over120-130 the front wheels get lighter and lighter and you can start to feel them "float". Not very comforting at two miles per minute. Spoilers and such on street driven production cars are added more for bling factor than actually helping the car cut through the air. There are some cars, like the new 350Z, that have had extensive work done, even underneath, to make the car slice through the air.

[rsiwicki]

I have seen the result of air pressure built up under the hood of a car as high speeds. I remember a C&D TV show with them testing the new C5 at the time and showing that at 170mph the hood on the C5 was actually bowed in the center about an inch above the lines of where it should be. I have never felt the front end lift, only back end lift while cruising at high speeds. From what I have read about lift...the rear spoiler is used to create more downward pressure on the back tires to keep from lift occurring there. Don't ask my why, but I have noticed this on the NASCAR when I do my arm chair watching and on SpeedVision they talk many times about the rear end lifting and never the front end lifting for which the rear wing they say is designed to create the down force needed on the back end. Ugghh!!!! I don't really care as long as I don't feel any lift going on when I am have the Q floored.

[Jesda]

I saw a video clip a couple years ago of an RX-7 at the Bonneville salt flats. It was traveling at over 200mph and the vehicle spun, the front lifted, then the rear, then the whole car took flight a few feet in the air and flipped around before it slammed top-down.

Here it is:http://www.gofastvideo.com/gal...i.wmv

Nice site for racing clips:http://www.gofastvideo.com/gallery/album/view/26

[rsiwicki]

its is too hard to tell in that video clip what was lifted first. Only the driver would know. The rearend could have easily lifted a little first causing the unstable steering up front. The car I was driving when I felt the rear end lift...you could literally feel the whole rear lift up while the front end was planted down causing the rear of the car to wiggle and make me almost lose control. I was so young and stupid...that me and my friends tried it again and we again felt the rear lift while the front was firmly on the ground. This was on a slower acceleration rate then most sports cars and my Q so that might have something to do with it that the rear end felt light first since the rate of acceleration was very slow. Eitherway...I am glad I have not experienced anything like this yet in my 3,960lbs Q.

[PoorManQ45]

Air piles up under the hood at speed, imagine a snow plow to help with the visual. Depending on the car at speeds over120-130 the front wheels get lighter and lighter and you can start to feel them "float".

Does this apply to the 90-93Q as it does to the 94+ Qs? The 90-93 model Qs don't have a grill. It would seem that it was designed like this for the purpose of lessening front end lift. From the way that the nose of the 90-93 Qs looks, to me, it would seem that it would actually generate a little downforce. I may and probably wil be wrong.

Also, to defeat front end lift, you can install an air splitter/dam on the lower bumper. Also, to further reduce lift, you can install side skirts. The less air that flows under the car, relative to the amount that is flowing over it, the less lift you will experience. If Less air is flowing under than over the car downforce would be created. This is caused by the low pressure zone that would exist under the car.

Ok engineers, I'm waiting for you to tell me how wrong I am.

[HeavyDuty]

I usually work on pushrod engines.

I believe that was an accurate assumption made by all parties. And yes, Greg has mentioned he wonders what the underside of your valve covers looks like.

Does the VH45DE use rocker arms? If so, what ratio are they?

No. DOHC, and you can't swap out for currently available 1.6's or 1.73's. Perhaps you could work on a new design though.

Also, to defeat front end lift, you can install an air splitter/dam on the lower bumper.

Awesome idea, then your car would have a *higher* top speed! Right?

[AZhitman]

Does this apply to the 90-93Q as it does to the 94+ Qs? The 90-93 model Qs don't have a grill. It would seem that it was designed like this for the purpose of lessening front end lift. From the way that the nose of the 90-93 Qs looks, to me, it would seem that it would actually generate a little downforce. I may and probably wil be wrong.

Also, to defeat front end lift, you can install an air splitter/dam on the lower bumper. Also, to further reduce lift, you can install side skirts. The less air that flows under the car, relative to the amount that is flowing over it, the less lift you will experience. If Less air is flowing under than over the car downforce would be created. This is caused by the low pressure zone that would exist under the car.

Ok engineers, I'm waiting for you to tell me how wrong I am.

Nope. You're actually pretty close to right.

Although those "skirts" will also add wind resistance, which will < top speed.

I wanted to see the underside of your valve covers to point out that if your Q is like most pre-owned Q's, it'll be pretty varnished and gummy (R.I.P. Wes's Q) and will therefore be utterly incapable of the speeds you claimed.

Better yet, let's see some 1/4 mile times.

[szh]

FWIW, I have cruised my 1991 Q for long distances at 140+mph (story is in the Infiniti speeding stories thread) back in 1992 (tires and car in perfect shape then.) I had to keep the accelerator pushed in hard to hit 160mph on level ground. Of course, all as indicated on the speedometer. I am convinced that my 1991 Q had a speed limiter, although I did not "feel" it operating in any way. It probably just prevented the TCU and ECU from acting upon my mashed foot commands of the accelerator! BTW, given that there is some slip, this means a probable speed of about 150 to 155mph maximum.

Car felt rock solid, without lift (Greg, I think you need to get that bottom cover back on!) of any kind. When I slowed down to 120mph, I drove with one hand lightly on the wheel - it felt that slow!

I do not recall taking my 1995 Q to those speeds for any length of time, as it felt a lot more floaty and unstable at higher speeds. Probably had more to do with the softer suspension than anything else, I would guess. PMQ, there is no way you have hit a real 160+mph in your Q. Simply not believable - sorry!

In my current M45, I have cruised for short distances at 125+mph or so, without any strain or lift or concern ... very reminescent of the 1991 Q. But, given that I have a kid now, and have to be more responsible, I am unlikely to ever repeat that long-distance high speed run that I did back in 1992! Oh, well!

Z

[PoorManQ45]

Car felt rock solid, without lift (Greg, I think you need to get that bottom cover back on!) of any kind.

I took the bottom cover off of my Q. IMO, it doesn't really make a difference. It may produce a little more lift, but nothing noticable.

PMQ, there is no way you have hit a real 160+mph in your Q. Simply not believable - sorry!

I think that we have established that speedometers are not accurate at high speeds. So, let me re-phrase my statement. I have hit 160+mph as stated by the speedometer.

I have a state trooper friend that drives a camero ss(pushing 400+hp) as his work car. I could see if he would be willing to clock me. I think that would give us a non-arguable speed. Because what the police clock you at is what really counts.

[rsiwicki]

I still can't get over all this debate on the top end speeds of our cars. I wish I was still an active SCCA driver and then I could contact a few people and go run my car at the Homestead speedway and have somebody clock my average lap speed to see how high we can go in our Q's. Hell I would like to just cruise at 140mph for a while to get a real feel for driving at those speeds versus the little sprint here and there.

[PoorManQ45]

I still can't get over all this debate on the top end speeds of our cars. I wish I was still an active SCCA driver and then I could contact a few people and go run my car at the Homestead speedway and have somebody clock my average lap speed to see how high we can go in our Q's. Hell I would like to just cruise at 140mph for a while to get a real feel for driving at those speeds versus the little sprint here and there.

That would be great. Driving around the track as fast as you can, and then getting the real top speed of the car. That would be a major adreniline rush, for me at least.

[maxnix]

I took the bottom cover off of my Q. IMO, it doesn't really make a difference. It may produce a little more lift, but nothing noticable.

Yeah, the truth is Nissan just had a bunch of these lying around the factory floor and decided to bolt them on to get rid of them.

Underbody airflow mangement is sooo overrated!

[Jesda]

Better airflow is also good for fuel economy on long trips.

[PoorManQ45]

Yeah, the truth is Nissan just had a bunch of these lying around the factory floor and decided to bolt them on to get rid of them.

That's what I think. It put off alot of black smoke when I burned it. It gave me a buzz.

Seriously though, I'm not saying that the under carriage didn't do anything. If you put it in a wind tunnel, you would probably see that it causes air to flow under the car faster. What i'm talking about are my personaly experiences. I have not noticed any lift on the front end. Maybe the drag is/was increased by .01, but doesn't make a difference to me.

Underbody airflow mangement is sooo overrated!

As long as the car doesn't lift off the ground(unintentionally) it's ok.

Actually, I was thinking about making some sheet aluminum panels to put on the underside of the car. To smooth things out, and increase air velocity under the car.

[russg]

I took the bottom cover off of my Q. IMO, it doesn't really make a difference. It may produce a little more lift, but nothing noticable.

Did your lobotomy change the aerodynamics of your forehead? Any noticable lift there? Possible explanation of why your feet never quite touch the ground?

[PalmerWMD]

The topic is locked

Fred