auszookers.com :: View topic - Will a decent exhaust improve my top speed?

I've just got my stock headers and exhaust on my 1990 Sierra at present. While i've got some extractors laying in the shed, I'm just waiting for the $$$ to build up so I can get the whole exhaust system sorted at once.

On a flat road my Sierra is faster than most (other Sierra's, that is!!!), but put an inclined road in my way and the ol' Sierra is slower than a grandma on a mountain bike.

Can I expect better top end speeds (moreso than just a negligible kph increase) with a decent exhaust setup?

I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... :wink:

MacBear wrote:

I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... :wink:

I actually run straight LPG as of last week - a higher octane rating than any petrol. You can really feel the extra punch of the gas right across the rev range, and I can sit on 120kph all day on a flat highway (I never got past 110k's on petrol). But, put the car on a hinterland road and I can struggle to sit on 80kph even in 4th gear.... just looking for a little more consistency at the top end.

Maybe just the quirks of a smaller engine?

I have now fitted ...... 8mm leads,....... new plugs and run her on 95 fuel (also did the tappets and flushed the oil)....

MacBear wrote:

I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... :wink:

che_guitarra wrote:

MacBear wrote:

I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... :wink:

you do realise that it is a 20 y/o 4wd with a 1.3ltr motor? i have had
motorbikes with bigger motors.

Ahhh ok, cool, i am guessing you know how to use the gas properly, you have to lubricate the valves and rings every now and then, by running it on petrol for a while...

If its struggling to reach 80kph, it sounds like your Carby needs some serious attention... :wink:

Not sure what i've said to indicate I want to be doing 120 up a mountain (?) ... just don't like massive drop off in speed whenever an incline is involved.

I can sit on 120kph all day on a flat highway (I never got past 110k's on petrol). But, put the car on a hinterland road and I can struggle to sit on 80kph even in 4th gear.... just looking for a little more consistency at the top end.

only money I would be spending right now is sticking it on a dyno and making sure its making the most amount of power at those revs as it can

but remember its a big box shaped thing with a pissy little underpowered engine in it, be happy you can hold 4th gear on any amount of slope

Author:	Che [ Sat Mar 27, 2010 5:49 am ]
Post subject:	Will a decent exhaust improve my top speed?
I've just got my stock headers and exhaust on my 1990 Sierra at present. While i've got some extractors laying in the shed, I'm just waiting for the $$$ to build up so I can get the whole exhaust system sorted at once. On a flat road my Sierra is faster than most (other Sierra's, that is!!!), but put an inclined road in my way and the ol' Sierra is slower than a grandma on a mountain bike. Can I expect better top end speeds (moreso than just a negligible kph increase) with a decent exhaust setup?

Author:	want33s [ Sat Mar 27, 2010 5:51 am ]
Post subject:	Re: Will a decent exhaust improve my top speed?
In theory a good exhaust will help but in the real world you are wasting your money that could be put towards something useful like mud tyres or a locker or a G16B conversion.

Author:	MacDaddy [ Sat Mar 27, 2010 6:58 am ]
Post subject:	Re: Will a decent exhaust improve my top speed?
che_guitarra wrote: I've just got my stock headers and exhaust on my 1990 Sierra at present. While i've got some extractors laying in the shed, I'm just waiting for the $$$ to build up so I can get the whole exhaust system sorted at once. On a flat road my Sierra is faster than most (other Sierra's, that is!!!), but put an inclined road in my way and the ol' Sierra is slower than a grandma on a mountain bike. Can I expect better top end speeds (moreso than just a negligible kph increase) with a decent exhaust setup? Yes and no... Your engine will give you more torque/power, but top end speed... maybe a little... it will get to that speed faster than it did without Extractors and a Sports exhaust system... you can expect up to 5hp more, but that would be optimistic... but even 3 more hp is better than nothing... When i had my 89 Vit with the G16A carby engine, i had Extractors and a 2in sports system fitted, and i could definitely feel an increased engine performance, and once i got to 4000rpm, there was an almost small Turbo like boost, that usually only comes from a tuned system, but my Vit really loved the sports system ! And as soon a i save enough, i will be getting Extractors and a sports system for my new V6 GV ! I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives...

Author:	Che [ Sat Mar 27, 2010 12:16 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
MacBear wrote: I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... I actually run straight LPG as of last week - a higher octane rating than any petrol. You can really feel the extra punch of the gas right across the rev range, and I can sit on 120kph all day on a flat highway (I never got past 110k's on petrol). But, put the car on a hinterland road and I can struggle to sit on 80kph even in 4th gear.... just looking for a little more consistency at the top end. Maybe just the quirks of a smaller engine?

Author:	shep [ Sat Mar 27, 2010 12:30 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
che_guitarra wrote: MacBear wrote: I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... I actually run straight LPG as of last week - a higher octane rating than any petrol. You can really feel the extra punch of the gas right across the rev range, and I can sit on 120kph all day on a flat highway (I never got past 110k's on petrol). But, put the car on a hinterland road and I can struggle to sit on 80kph even in 4th gear.... just looking for a little more consistency at the top end. Maybe just the quirks of a smaller engine? you do realise that it is a 20 y/o 4wd with a 1.3ltr motor? i have had motorbikes with bigger motors.

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Author:	Woody [ Sat Mar 27, 2010 1:38 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
I have only had my '91 and found I was never using 5th gear. After reading the article on how to get 20% more power from your engine in 4WD Custom Guide No 23, I have now fitted extactors and a 2" straight through exhurst, POD air filter, 8mm leads, Bosch hi volt coil, new plugs and run her on 95 fuel (also did the tappets and flushed the oil). She goes like a cut snake now and I can even short shift from 3rd to 5th and cruse around at 60kph in 5th if I want. Added bonus is it sounds awsome when you put the boot in or back off but as someone else said you don't get any better top end you just get there quicker.

Author:	atari4x4 [ Sat Mar 27, 2010 3:42 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
the POD filter isn't an ideal set up for a 4wd that gets used off road.

Author:	want33s [ Sat Mar 27, 2010 4:35 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
Woody wrote: I have now fitted ...... 8mm leads,....... new plugs and run her on 95 fuel (also did the tappets and flushed the oil).... This is what has made the noticeable difference in power... Nothing else. Probably all it ever needed was a good tune and service. Oh and good luck with the pod filter... You'll find your oil consumption will increase real soon.

Author:	MacDaddy [ Sat Mar 27, 2010 5:31 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
che_guitarra wrote: MacBear wrote: I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... I actually run straight LPG as of last week - a higher octane rating than any petrol. You can really feel the extra punch of the gas right across the rev range, and I can sit on 120kph all day on a flat highway (I never got past 110k's on petrol). But, put the car on a hinterland road and I can struggle to sit on 80kph even in 4th gear.... just looking for a little more consistency at the top end. Maybe just the quirks of a smaller engine? Ahhh ok, cool, i am guessing you know how to use the gas properly, you have to lubricate the valves and rings every now and then, by running it on petrol for a while... If its struggling to reach 80kph, it sounds like your Carby needs some serious attention...

Author:	MacDaddy [ Sat Mar 27, 2010 5:36 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
shep wrote: che_guitarra wrote: MacBear wrote: I would also change from standard unleaded fuel, to premium unleaded, the zook engines love that little extra octane rating, and it burns cleaner in the engine... less additives... I actually run straight LPG as of last week - a higher octane rating than any petrol. You can really feel the extra punch of the gas right across the rev range, and I can sit on 120kph all day on a flat highway (I never got past 110k's on petrol). But, put the car on a hinterland road and I can struggle to sit on 80kph even in 4th gear.... just looking for a little more consistency at the top end. Maybe just the quirks of a smaller engine? you do realise that it is a 20 y/o 4wd with a 1.3ltr motor? i have had motorbikes with bigger motors. I had 2 Sierra's, with a 1ltr and a 1.3ltr, and i had no trouble doing 110kph or more in both of them... My old Vit was 21 years old, it was quite zippy to start with, but when i put the extractors and 2in system on it, it really flew...

Author:	shep [ Sat Mar 27, 2010 5:42 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
the op wants to do 120 up a mountain. not gunna happen.

Author:	eldo [ Sat Mar 27, 2010 6:27 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
i took my zook on her maiden voyage yesterday, 497km in a day. it has a 2 inch sytem on it. i got 9.3L/100KM out of it and i sat on approx 110 all the way up to wyong from wollongong and back. on the hills i was back to 80 occasionally in 4th and even 3rd if i got stuck behind a truck etc and if you have been along the M3 you will know how big the hills are, this was only if i was a little lazy at the bottom, was also hot out side so i wasnt pushing it too hard. i hit speeds of 130 ish by accident, wasnt paying attention for a minute or 2. the engine only has 85000km on it and it is an unleaded donk from a 91 model. i did notice that when i ran some V power from shell it was a little better. i will be running it on standard pulp as thats what i generally get. however when i do go to a caltex it will be getting vortex, i dont think the exhaust is going to help you alot with what you want, i think it will help you throughout the rev range, but it is no magic bullet if you know what i mean. i am about to do a major service on it and hopefully put in a GT40 coil and new leads etc plugs etc etc.

Author:	Che [ Sat Mar 27, 2010 6:52 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
MacBear wrote: Ahhh ok, cool, i am guessing you know how to use the gas properly, you have to lubricate the valves and rings every now and then, by running it on petrol for a while... If its struggling to reach 80kph, it sounds like your Carby needs some serious attention... I'm running straight LPG, not dual fuel... not quite the same thing, as there's no need for a compatability compromise between the two fuels. Carby is nothing more than a throttle body in my case. Like I said, goes great on a flat highway, will sit on 120kph all day (that's prob more like 130 due to the larger tires messing up true speedo reading) - but take the flat road away, and even the most gentle hill gradients take a massive toll on the top speed... what i'd give to maintain 90 - 100kph on hill roads Not sure what i've said to indicate I want to be doing 120 up a mountain (?) ... just don't like massive drop off in speed whenever an incline is involved.

Author:	royce [ Sat Mar 27, 2010 7:03 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
only money I would be spending right now is sticking it on a dyno and making sure its making the most amount of power at those revs as it can but remember its a big box shaped thing with a pissy little underpowered engine in it, be happy you can hold 4th gear on any amount of slope

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Author:	shep [ Sat Mar 27, 2010 7:10 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
che_guitarra wrote: Not sure what i've said to indicate I want to be doing 120 up a mountain (?) ... just don't like massive drop off in speed whenever an incline is involved. uumm here. che_guitarra wrote: I can sit on 120kph all day on a flat highway (I never got past 110k's on petrol). But, put the car on a hinterland road and I can struggle to sit on 80kph even in 4th gear.... just looking for a little more consistency at the top end. you will get better gains in power by changing your gearing especially if you have bigger tyres.

Author:	SuziBlu [ Sat Mar 27, 2010 7:30 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
royce wrote: only money I would be spending right now is sticking it on a dyno and making sure its making the most amount of power at those revs as it can but remember its a big box shaped thing with a pissy little underpowered engine in it, be happy you can hold 4th gear on any amount of slope Royce, I drove 800k to get my big block dynod by the "highly recommended" man, cost a bucket load, on the way home, less power, more fuel, totally sukd, drove it to my mechanic and had to eat humble pie and ask him to retune it. I agree, its a shoe box shape, 120k is excellent, even with a tail wind, be happy.

Author:	eldo [ Sat Mar 27, 2010 9:47 pm ]
Post subject:	Re: Will a decent exhaust improve my top speed?
what size tyres are you running? it might be geared to high. maybe put a set of NT centres in it?? my car rins 215 s on the standard rims with the 3.9NT centres. i really think you might be asking too much from the 1.3. i basically have a new engine with the 80 odd thousand km on it and i still get back to 80 on a hill. gearing will definately help but i reckon you should ask someone that has owned a sierra from new, i bet they describe hill climbs the same as you have above even with a new vehicle.