X Pipe vs Headers
#16
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There's no doubt that some more power and smoother running can be achieved with SharkTuning a stock spec car. Louie did some work on such a car some while ago, and I think the gains were about 10HP for the LH tune and another 10 or for the EZK tune.
An X pipe fitment also would benefit, but I don't have any figures for before and after.
Fitting headers definitely requires a SharkTune to get the best out of the potential of that setup.. in my experience. They seem to lean out the top end.
An X pipe fitment also would benefit, but I don't have any figures for before and after.
Fitting headers definitely requires a SharkTune to get the best out of the potential of that setup.. in my experience. They seem to lean out the top end.
#17
Three Wheelin'
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Hi Tom,
I second Greg's comments and always consider your posts highly interesting and very detailed.
I have been redaing this through and maybe missed it but what is the difference between the GT with x-pipe and the same but after shark tuning the EZK and ECU?
I'm curious since I have the x-pipe and wonder how much more there is to possibly gain from sharktuning on top of this?
There is a person in the Swedish 928 club that have a Sharktuner but no dyno unfortunately, how far will the autotune option enabled on open road driving possibly help?
Maybe impossible questions to answer but curious if you have an idea.
/Peter
I second Greg's comments and always consider your posts highly interesting and very detailed.
I have been redaing this through and maybe missed it but what is the difference between the GT with x-pipe and the same but after shark tuning the EZK and ECU?
I'm curious since I have the x-pipe and wonder how much more there is to possibly gain from sharktuning on top of this?
There is a person in the Swedish 928 club that have a Sharktuner but no dyno unfortunately, how far will the autotune option enabled on open road driving possibly help?
Maybe impossible questions to answer but curious if you have an idea.
/Peter
Judging from what I have seen a GT with X pipe will make about 315 rwhp. Sharktune and you should see about 10 more or around 325. Sharktuning will also help the low and mid range a lot so the help is felt more in torque in the RPM range normally used than in absolute top end numbers. These are just generalities since there are difference in engines, cam timing, and MAF aging that will affect it.
When I put the headers on this car and tried to Sharktune, I had a really hard time of it and saw no gain from the headers. From that, you could safely say that a Sharktune for an X pipe isn't correct for headers. I should add that the problem I had wasn't due to the Sharktuner, but other things. One was that the WOT switch quit working. The other was that I could not get much correlation between the dyno O2 sensor (mounted in the tailpipe) and the wide band (mounted in the X) that fed the Sharktuner. I didn't know which to believe. The car has an adjustable FPR and I thought for a while that it was changing fuel pressure on us. Finally, I ran out of time and gave up. Later, while doing some other work on this car, I noticed that the exhaust joint between the outlet of the X and the rear exhaust wasn't tight. I think that was admitting some air into the exhaust and messing up my tailpipe O2 readings. I've become quite sceptical of mixture readings taken at the tailpipe. The owner removed the intake and replaced the throttle switch as well as the idle valve and generally refurbished everything. This time, I only relied on the Sharktuner O2 sensor readings and the tuning session went really well.
The Sharktuner Autotune feature is helpful for me when going to larger injectors, but otherwise I don't use it much. I find that on Autotune, the map will have a large (either + or-) right next to small numbers. I don't think that is right for final tune. The LH seems to have some averaging function that takes the value of adjacent cell numbers into account to calculate the final pulse width. This would be especially important when operation is near a border between cells. What I'm trying to say is that you could get a map to work with a big number next to a small number because of the averaging function. However, if you manually smooth out the map numbers, you'll see less of the wild fluctuations in O2 % correction as you move around the map. I have manually edited those large number changes between cells and did Autotune again and that sometimes helps. Each Autotune session usually results in different cell numbers. I'd do several autotunes and try to average out the cell numbers between sessions and you should get pretty close. Especially watch where large changes occur between cells.
I spend hours driving on the (inertia) dyno moving around the map approaching cells from low RPM to higher RPM, from lower load to higher load, and vice versa. At lower RPM and loads, I'll use the car brake and throttle to get to a particular cell, at higher rpm/load, I'll use the dyno brake and throttle. I monitor the O2 correction % and try to keep corrections to around +/-3%. Pretty soon the map begins to smooth out. The map number differences between adjacent cells are usually less than 15. The entire map will be within +/- 50. At least that is the goal. I spend a lot more tuning time at idle and up to 2500 rpm than time above that. All this work probably makes no difference at all on peak hp or tq numbers, but I think it gives a smoother running engine. This is just the way I do it. I usually don't log anything when tuning mixture and closely watch what happens in real time. I also zero out all the WOT map values and tune WOT on the main map.
Tuning timing is a whole 'nother story.
#18
Supercharged
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louis,
my friend recently fitted the 928 international headers to his 90 GT and there is a noticeable difference over the X pipe he had fitted. on my car i fitted new camshafts at the same time as headers and gained 30 bhp over just the X pipe, but i still need to shark-tune.
do you know if you can still get to the clutch with the devek headers in place? these are the headers on my car at the moment, i also have a spare set which i was thinking of using as a basis for some RHD sets.
my friend recently fitted the 928 international headers to his 90 GT and there is a noticeable difference over the X pipe he had fitted. on my car i fitted new camshafts at the same time as headers and gained 30 bhp over just the X pipe, but i still need to shark-tune.
do you know if you can still get to the clutch with the devek headers in place? these are the headers on my car at the moment, i also have a spare set which i was thinking of using as a basis for some RHD sets.
Sadly, I regret to inform you that a band of thieves broke into my house and stole the headers you were storing in my basement... This appears to be the only thing they took. The local police are involved. Should they locate your property, I will inform you (... eventually). I am truly sorry for your loss.
BTW, the CF hood is still there.
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#19
Three Wheelin'
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#20
Three Wheelin'
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#21
Three Wheelin'
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In other words, just slapping the headers on the car will not yield much of an improvement, correct? In order to benefit from the addition of the headers, you need to sharktune the car?? I already have the X-pipe, but did not consider the headers due to the post suggesting that there was no power gain or advantage. I am mechanically challenged, and would depend on my local 928 mechanic.
#23
Three Wheelin'
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By Louie
<snip>
As to the intake tracts, on the 2 Valver if I cant them outwards, i.e towards the fenders/guards they will be straighter, just a little difference between the two and four valve engines. I will try to get another inch or 2, as my engine will have another 1000 rpm 11 inches may be O.K but I want to make sure that there is enough clearance in front of the trumpet. Don't want to create a scenario like Porsche did with the S4 manifolds.
<snip>
As to the intake tracts, on the 2 Valver if I cant them outwards, i.e towards the fenders/guards they will be straighter, just a little difference between the two and four valve engines. I will try to get another inch or 2, as my engine will have another 1000 rpm 11 inches may be O.K but I want to make sure that there is enough clearance in front of the trumpet. Don't want to create a scenario like Porsche did with the S4 manifolds.
<snip>
I totally agree with the trade off, my car can easily light the tyres now so I don't want to even go there when another 50% more power is added. So it ends up heavier! Everything I can send to the back I will. The other thing I want to do, is add a flat floor with diffuser, I plan on putting NACA ducts into it and use various aero techniques used in F1 to pull the air through the coolers. In reality it is not that hard to implement but may be hard to get it to work correctly. I will get to find out in time I suppose.
I totally agree with the trade off, my car can easily light the tyres now so I don't want to even go there when another 50% more power is added. So it ends up heavier! Everything I can send to the back I will. The other thing I want to do, is add a flat floor with diffuser, I plan on putting NACA ducts into it and use various aero techniques used in F1 to pull the air through the coolers. In reality it is not that hard to implement but may be hard to get it to work correctly. I will get to find out in time I suppose.
Going back to the throttles for a second, are you happy with your idle? What does your car idle at? You will have more power than me, that is for sure but I want to be able to idle mine at a 1000 rpm or less, I do have a pretty big cam I was wondering if you are happy in this regard?
Cheers Greg
Cheers Greg
#24
Three Wheelin'
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Thanks for posting Louie. I have a set of MSDS 1 5/8" headers from Abby that I will be installing with a single 3 1/2" exhaust and a larger crank pulley for a couple pounds more boost. I will dyno before and after the exhaust change but probably not before and after the pulley change only as I don't want to spend the money. I don't understand why the collectors are 3" instead of 2 1/2". I will be using a Burns Stainless Y dual 3" into single 3 1/2". If I had the time and money it would be nice to try and fit a long transition from the 3" to 2.5".
I think the reason the collectors are 3" is so the primary pipes have an end; a discontinuity to generate the pulse travelling back up the pipe. A 2.5" collector may not be large enough plus the primary pipes would have to be squashed at the end to fit in a 2.5" collector. The MSDS headers are not anything close to equal length so I don't know if the tuning matters much or even may be an impediment at some RPMs. I just don't know. Your 3" to 3.5" Y should take care of any transition from the 3" collectors. Guess you'd need a short 3" piece of tubing to connect to the Y.
#25
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Could you use a curved runner? Have the runner curve inward toward the valve as it enters the port. Then as it moves away from the port curve inward toward the center toward a common plenum. Seems like the 2v motors have at least a couple more inches of height between the head and underside of the hood. Might work.
![](https://i7.photobucket.com/albums/y261/gjm123/V06.jpg)
This was the only way to fit throttle bodies and have them fit under the standard bonnet.
Please forgive me if I've misunderstood, but could something like this work?
I'm enjoying the discussions - thanks guys. (Greg and I have exchanged some emails - he's written, I've read and learnt, and then asked more questions...)
Graham
#26
Three Wheelin'
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I used to drive 2.5 V6 Vauxhall (GM) fitted with a Jenvey set up; it looked like this:
![](https://i7.photobucket.com/albums/y261/gjm123/V06.jpg)
This was the only way to fit throttle bodies and have them fit under the standard bonnet.
Please forgive me if I've misunderstood, but could something like this work?
I'm enjoying the discussions - thanks guys. (Greg and I have exchanged some emails - he's written, I've read and learnt, and then asked more questions...)
Graham
![](https://i7.photobucket.com/albums/y261/gjm123/V06.jpg)
This was the only way to fit throttle bodies and have them fit under the standard bonnet.
Please forgive me if I've misunderstood, but could something like this work?
I'm enjoying the discussions - thanks guys. (Greg and I have exchanged some emails - he's written, I've read and learnt, and then asked more questions...)
Graham
#27
Three Wheelin'
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<snip>
I know we have discussed this before but what was the length used for the intake tract? For my engine I am using the 2V engine I am able to comfortably able to get 10" runner to the back of the valve without canting the intake runner I can get more by angling it but I would like to keep it straight for max flow.
<snip>
Cheers Greg
I know we have discussed this before but what was the length used for the intake tract? For my engine I am using the 2V engine I am able to comfortably able to get 10" runner to the back of the valve without canting the intake runner I can get more by angling it but I would like to keep it straight for max flow.
<snip>
Cheers Greg
I measured a TB length (3.5") and air horn (2.75"). That gives a total length of 6.25". The adapters add about an inch average. The port is about 4". Looks like a total of 11.25". The air horns are bell mouthed which I understand makes their effective length shorter than their physical length. I did cut the air horn for cyl #1 a quarter inch shorter than the rest because that air horn top was quite close to the air box top. The power is no different with the box top on or off so apparently that air horn isn't smothered by proximity to the top.
#28
Drifting
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john, interesting observation about lean running with headers.. ive got a dyno with the whole air fuel getting richer and richer! mind you this is with the map we had previously set up for the exhaust with louis X pipe.
andrew - will your insurance cover the £1000 i paid for those headers?![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
does anyone know if you can get at the clutch with the devek level two headers on the car??
andrew - will your insurance cover the £1000 i paid for those headers?
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
does anyone know if you can get at the clutch with the devek level two headers on the car??
#29
Three Wheelin'
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#30
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Greg was referring to the profile of the intake trumpet, not its cross-section.
An article in Race Engine Technology magazine tested several trumpet profiles (elliptical, circular, "aerofoil" and a plain pipe end) to determine which yielded the best mass flow and pressure recovery. The elliptical bell profile was found to be the best (the cross-section of the duct and bell mount was circular).
For a duct diameter, d, the best ellipse shape had a mouth of diameter 2.13d, and length (from the lip (ie normal to the direction of the duct) to where it necked down to the duct diameter) of d (hence Greg's description of "short and fat". There also was a radius outboard of the lip (leading edge) to smooth the flow of air being ingested from the side. I don't recall how much effect that radius was found to have.
In the article, the duct used for the tests was 23mm in diameter, so the mouth of the optimum elliptical trumpet profile was 49mm (2.13d) in diameter, length 23mm and the radius outboard of the lip was (I think) 3 mm (so 0.13d if I remember correctly).
An article in Race Engine Technology magazine tested several trumpet profiles (elliptical, circular, "aerofoil" and a plain pipe end) to determine which yielded the best mass flow and pressure recovery. The elliptical bell profile was found to be the best (the cross-section of the duct and bell mount was circular).
For a duct diameter, d, the best ellipse shape had a mouth of diameter 2.13d, and length (from the lip (ie normal to the direction of the duct) to where it necked down to the duct diameter) of d (hence Greg's description of "short and fat". There also was a radius outboard of the lip (leading edge) to smooth the flow of air being ingested from the side. I don't recall how much effect that radius was found to have.
In the article, the duct used for the tests was 23mm in diameter, so the mouth of the optimum elliptical trumpet profile was 49mm (2.13d) in diameter, length 23mm and the radius outboard of the lip was (I think) 3 mm (so 0.13d if I remember correctly).