akshay67

Whats the safest highest speed that you can cruise at in a MY99 Turbo (for say 1 hour)?
By 'safest' i mean something that the prevents the engine from blowing up.

john banks

They have a speed limiter at about 144 mph anyway if you are using the original ECU for boost control.

I would suggest 120-130mph but you will use a lot of fuel.

LG John

To keep the right to drive then its 70mph I'm affraid

I find to drive over 100mph the car has to be on boost nearly all the time so that is bound to heat the turbo, etc up?

john banks

That is because you have a Dawes on your car Kenny - gives more part throttle boost.

Iain P

I have noticed that the intercooler temps rise significantly over about 100mph. Not sure if this suggests bad flow thro' the intercooler or just reflecting boost temps. I would have thought that fitting a temp sensor would be wise so it can be monitored. I think 50 deg plus is the max? I get around ambient temps for the intercooler-out air up to about 80mph. At 90-100 it's about 10 degrees higher. Water spray makes a big difference to temps at these speeds!

Pavlo

my legacy has a charge cooler with it's rad in the front. there was talk about the flow on the bonnet skipping over the IC at high speed

Ali Scott

144mph limited to on the ECU??

Had my speedo reading 152Mph at the weekend, virtually standard MY97 Turbo, was still way off the red-line..

ozzy

don't believe your speedo reading, it'll be over reading by some margin. The rev limiter will still be there, although wind and downhill runs will affect the overall top speed.

Stefan

Ali Scott

yeah, was down a slight hill this time..

regularly had her up to 145-147Mph and no sign of a rev limiter.

Hoppy

Unknown territory, I think. And there have been numerous reports of engine failure after high-speed running. But if your motor's sweet and full of good oil, fit an oil temp gauge, EGT gauge and KnockLink. As long as they read okay, you can probably keep going. I doubt if you'll last an hour on a tankful, though

However, on a track day thrash things usually start getting very hot after 15 minutes or so (at 7 mpg). And you will rarely top 120 mph there. As Pavlo says, there are questions over the effectiveness of the intercooler scoop at high speed, and I would be concerned about stability over 140-ish in anything but a straight line (aerodynamic lift and stock suspension).

Richard.

swaussie

Agree with you there John, My car will read off the clock at over 260kmh on an Autobahn but its limited to 248.

NENO

Speedo's only have to accurate to 10% which means that at 140 you could be reading as high as 154, quite a large margin. It's my opinion that the vast majority of manufacturers deliberately make there speedo's over read. Based on me checking the three cars I've owned since I got a speed gun!

As for safe cruising speed, I had my best fuel ecomony ever cruising at 95mph on way over to Germany the other week.

MorayMackenzie

"It's my opinion that the vast majority of manufacturers deliberately make there speedo's over read. Based on me checking the three cars I've owned since I got a speed gun!"

I assume thats three cars each from a different manufacturer... hum. I would suggest that there are significantly more than three car manufacturers out there, so this isn't exactly conclusive in any way, even if you did buy yourself a speed gun.

I believe the British Law, or at least the traffic policing guidelines used to enforce said law, tend to allow up to 10% tolerance for car instrument error.

Manufacturers do indeed tend to err on the side of caution with regards to speedo accuracy. Most cars I have driven and tested (timed at set indicated speeds over measured mile) tend to be up to 12% overreading on the speedo, which is, of course, safer for the users license. Of course, speedo accuracy will be affected by tyre wear and pressure, and anything else that might affect rolling radius on the wheels, such as a non-exactly matched change of wheel size.

RB5_245

quote british law allows for 10% LOL, "it ok sonny you were only doing 140, try to keep the speed down a bit eh, now on your way"

Adam M

according to an inventor client from fords, they have a range of 10% accuracy to play with when they buy in the components from their suoppliers. This gives them from -0 + 10 to -10 +0.

Most spec to over read by 10%.

vindaloo

ISTR that speedos have to read between +3 and +9 optimistic by law. They definitely not allowed to underestimate your speed.

Vindaloo.

CataIunya

Yeah I heard the same they are not allowed to under read but are allowed upto 10% over read.

MorayMackenzie

RB5_245,

"quote british law allows for 10% LOL, "it ok sonny you were only doing 140, try to keep the speed down a bit eh, now on your way"
"

Okay, you are "quoting" from two different posts in two different contexts. I mentioned the 10% by law, or guidelines in applying the law in my own post, whereas the Neno post I quoted talked about speeds of 140. I dont understand how you manage to tie up a speed of 140 and the british law allows 10% in your "quote".

NENO

Moray I just love your tone

And to confirm that these three cars were from different manufacturers, VW, BMW and Subaru. I mentioned the three because I didn't want anyone thinking this was a conclusive test that I had carried out just three cars I've owned.

Paul_M

They always over-read cos it's illegal to under-read and they ain't gonna calibrate every speedo to be totally accurate. So they're designed to over-read to allow for tolerances which will never cause one to go under the threshold (in theory anyway ).

Hol

iTrader: (1)

The oil starts to get hot as you go over 4500rpm

Thats only 90mph in my car and 112 in yours.

MorayMackenzie

NENO,

I assume you didn't see the smilies I used.

I was also agreeing with your main point, just from another standpoint.

Moray

NENO

Thanks Moray, I did see the smilies. It was your withering tone and veiled disbelief that was making me smile.

I'd be interested to know from what source people say the 10% only counts one way - I understood that it was 10% plus or minus on a given speed.

NACRO

As far as the speedo thing goes I had an indicated 150 on my speedo during a recent trip to Europe- GPS and road markers seemed to indicate the car was doing more like 142mph so I reckon thats accurate enough.

I cruised for a sustained 200 miles at an indicated 120mph and the car didn't seem any hotter than usual. This was part of a 550 mile stint all done at high speed on a mixture of A roads and Mways. The car didn't miss a beat, get excessively hot or use any oil. FYI its a MY97 UK Turbo with no mods.

neil@wrx

cruised at 115 for 4.5hr in spain got 15.5 mpg in a 93 WRX 6000rmp!!!!!!

Ali Scott

115mph @ 6000rpm ??

Were you in 4th gear or something? Mine does a ton @ 4000rpm as do most I imagine??

Anyone else?

neil@wrx

12 month a go got P1 now may be it was less who gives a tos it went bang 4 month later on the dealer i sold it to but i still like the old girl more then the P1 sum times

[Edited by neil@wrx - 5/14/2003 7:54:46 PM]

MorayMackenzie

NENO,

RE "I'd be interested to know from what source people say the 10% only counts one way - I understood that it was 10% plus or minus on a given speed."

[non withering tone on]

Okay... I don't actually know of anywhere in the UK with a Mandatory _Minimum_ Speed Limit.

("Curb-crawling" being a completely unrelated offence, before anyone suggests that )

[non withering tone off]

swaussie

In Victoria Australia they are talking about implementing zero tolerance on speeding - 1 km/h over the limit and you can be fined. The argument is that speedo's all read fast so it should not be a concern if you stick to the indicated speed limit as shown by your speedo. South Africa has also mentioned doing this I believe?

Another topic under discussion is having two cameras placed a known distance apart and taking photos of each and every number plate that passes through. So if they are 100km apart and you arrive at the next one in 50 minutes they know you have been doing more than 100km/h ? Very big brotherish, unless you pull over for a break every 15 mins and drive like crazy between breaks

nom

The cameras a few miles apart taking averages is already in use over here
Can't see the point in the zero tolerence thing - staying at the wrong set speed (so 40 when a 60 would be the right one for sight/road conditions/traffic quanitity/number of turnings/lack of pedestrians) takes a lot of concentration.
It appears it's 'a bad thing' to be doing a very alert 35mph & avoid hidding a drunk pedestrian as you're watching the road, but 'a good thing' (& safe...) to be staring at the speedo 40% of the time & so hit the errant pedestrian. Eh?

Anyway... safest highing cruising speed I think was the point... doesn't it depend rather on the set up of the car? As in gear ratio, charge temperature, the particular fuel's resistance to knock at elevated temperatures & stuff? Whack on an oil temp gauge, EGT & KnockLink, keep an eye on them & go for it I'd have thought is the answer