Jack Houpe
GT40s Supporter
Great pictures Mike, are you going to find a low pressure point on the collector to evacuate the crankcase? I have been meaning to ask you this, I know it worked well on the pantera.
Pairing headers?
- Thread starter Peruch
- Start date
No, the vacu-pan system, if installed properely, works well with carburated engines but you can't use it on injected engines that uses an O2 sensor. The O2 sensor needs to be at or near the same location and the extra oxygen being injected into the exhaust will destroy the readings from the O2 sensor. This is true even if the O2 sensor is somehow up stream from the vacu-pan fitting due to reversions in the exhaust system. Can't use O2 sensors on carburated engines either that have vacu-pan systems except for tuning and you must cap the vacu-pan system during tuning.
So, Mike, or anyone,
For tuning on a carburetted GT40 engine, bearing in mind oxygen from the slip joints in the collectors, where should the O2 sensor be located?
Cheers
For tuning on a carburetted GT40 engine, bearing in mind oxygen from the slip joints in the collectors, where should the O2 sensor be located?
Cheers
Russ:
If you are using a four barrel carb there is no reason to not put the sensor anywhere other than in or just after the choke on the collector.
If it is a Weber style it would be great to have one in each cylinder just after the port for tuning and then monitor the system with one in the collector.
You could also use one in each port for initial turning on a four barrel as well and tune the carb to the lean cylinder. Might save a piston down the road.
A practical alternate would be to have EGT's in each port that you could run all of the time and monitor the engine. You could then monitor the whole enginer and control a closed loop system with the O2 sensor in the collector.
The logical solution is just an O2 bung in each collector. One for the ECU and one for monitoring and initial tuning.
Now the question about the slip joints on the headers is a very important point. It is also important to have thick header flanges at the ports to insure that they do not warp and allow oxygen in. Here is what I recommend.
1. If the collector to primary pipe intersection is done properly the primary pipe end should be square and seat into the collector right at the point of expansion of the pipe in the collector. This can actually provide a leak free joint if done properly. The double-slip joints as used on many turbo applications will also enhance this.
2. With the above done properly I recommend the "bung" style tabs in lieu of the overlapping type tabs. This allows you to actually pull the primary into the collector expansion seat. It also allows you to have two nuts on the treaded shaft between the lugs that allows you to expand the collector apart for dismounting. You can see these tabs at www.burnsstainless.com/hardware/tabs-O2-rings/tabs-o2-rings.html.
I hope I typed all of that right. This arrangement will also keep the primary tube from trying to back out of the collector when the motor heats up much better than the sheet metal type lugs which flex. Point is use the tube type.
3. If the headers are going to use O2 sensors I always use the V-band type clamps between the collector and whatever the tail pipe might be. It is almost impossible to get a good seal on a large diameter tube slip joint.
4. If your existing collectors have the primary pipes far enough apart where they enter the collector I have had good luck doing this. Get some of the 1 or 2 inch wide header wrap material and wrap the primary tube right up next to where it enters the collector. Then take some very thin stainless sheet metal that is almost foil thickness and wrap this joint with at least a half diameter overlap. Use two quality hose clamps and secure in place and you have a sealed joint. This obviously doesn't look very trick but it will get you through tuning of the engine and then you can take it off.
If you don't do the above, forget using O2 sensors.
If you are using a four barrel carb there is no reason to not put the sensor anywhere other than in or just after the choke on the collector.
If it is a Weber style it would be great to have one in each cylinder just after the port for tuning and then monitor the system with one in the collector.
You could also use one in each port for initial turning on a four barrel as well and tune the carb to the lean cylinder. Might save a piston down the road.
A practical alternate would be to have EGT's in each port that you could run all of the time and monitor the engine. You could then monitor the whole enginer and control a closed loop system with the O2 sensor in the collector.
The logical solution is just an O2 bung in each collector. One for the ECU and one for monitoring and initial tuning.
Now the question about the slip joints on the headers is a very important point. It is also important to have thick header flanges at the ports to insure that they do not warp and allow oxygen in. Here is what I recommend.
1. If the collector to primary pipe intersection is done properly the primary pipe end should be square and seat into the collector right at the point of expansion of the pipe in the collector. This can actually provide a leak free joint if done properly. The double-slip joints as used on many turbo applications will also enhance this.
2. With the above done properly I recommend the "bung" style tabs in lieu of the overlapping type tabs. This allows you to actually pull the primary into the collector expansion seat. It also allows you to have two nuts on the treaded shaft between the lugs that allows you to expand the collector apart for dismounting. You can see these tabs at www.burnsstainless.com/hardware/tabs-O2-rings/tabs-o2-rings.html.
I hope I typed all of that right. This arrangement will also keep the primary tube from trying to back out of the collector when the motor heats up much better than the sheet metal type lugs which flex. Point is use the tube type.
3. If the headers are going to use O2 sensors I always use the V-band type clamps between the collector and whatever the tail pipe might be. It is almost impossible to get a good seal on a large diameter tube slip joint.
4. If your existing collectors have the primary pipes far enough apart where they enter the collector I have had good luck doing this. Get some of the 1 or 2 inch wide header wrap material and wrap the primary tube right up next to where it enters the collector. Then take some very thin stainless sheet metal that is almost foil thickness and wrap this joint with at least a half diameter overlap. Use two quality hose clamps and secure in place and you have a sealed joint. This obviously doesn't look very trick but it will get you through tuning of the engine and then you can take it off.
If you don't do the above, forget using O2 sensors.
Gents,
sorry, I have to come back to the original topic of the thread. Can anybody of you tell if a 180° tri-y exhaust header souds much different than the crossover system?
I am planning on building such a system on my project, as space is very limited in the top and I think that a tri y header requires much less space.
The only thing I am afraid of is that the v8 loses its characteristic sound.
Hope someone can help,
thanks
sorry, I have to come back to the original topic of the thread. Can anybody of you tell if a 180° tri-y exhaust header souds much different than the crossover system?
I am planning on building such a system on my project, as space is very limited in the top and I think that a tri y header requires much less space.
The only thing I am afraid of is that the v8 loses its characteristic sound.
Hope someone can help,
thanks
David Morton
Lifetime Supporter
Ian,
Tony Law near Leeds
Contact Information
<TABLE id=contacttab cellSpacing=0 cellPadding=0 border=0><TBODY><TR><TD>Tony Law Exhausts
Mr. P Walton
Unit 3 Queen Street
Stourton
LEEDS
LS10 1SL(Map).
Tel: 0113 2715422 Fax: 0113 2715422
Mobile: 07802487046
Email: [email protected]
Or alternatively you can email us via this form.
</TD></TR></TBODY></TABLE>
Tony Law near Leeds
Contact Information
<TABLE id=contacttab cellSpacing=0 cellPadding=0 border=0><TBODY><TR><TD>Tony Law Exhausts
Mr. P Walton
Unit 3 Queen Street
Stourton
LEEDS
LS10 1SL(Map).
Tel: 0113 2715422 Fax: 0113 2715422
Mobile: 07802487046
Email: [email protected]
Or alternatively you can email us via this form.
</TD></TR></TBODY></TABLE>
Leopold,
Since no one else has answered you....By definition a conventional tri y cannot be a 180° system, you have to go crossover for that. A tri y will give you that traditional V8 beat common to the majority of american V8s. The sound is totally different to the traditional 180° crossover system used on most GT40s .
A tri y will usually yield better mid range power at the expense of some top end loss compared to ordinary 4 into 1s on each bank.
Last edited:
You CAN build a 180° tri y system simply by connecting the appropriate cylinders, BUT the primarys will be longer than desirable due to having to pass under or over the engine to couple at least two pairs of cylinders, at that point you will find you have a fairly messy looking system and a crossover or conventional 4 into 1 per bank will start to look better. Bite the bullet & make it 8 into 1, thats the best system all round.
And of course a 180° tri y COULD easily be built using a flat plane crank! The chance of that being an option is probably higher than having pipes running under or over the engine, since he says he is considering the tri y as he is constrained for space! I think he meant a conventional 4-2-1 on each bank not a complex 180° setup.
BTW have you ever seen a 180° tri y?
BTW have you ever seen a 180° tri y?
Yes, every second set of headers I built for Anglias/Cortinas etc was a tri-Y setup and they were ALL flat plane cranks
Ha bloody ha! You missed your calling Jac Mac, you should have been a lawyer!!!:lipsrsealed:
Its not too late in the day yet, and if some of the customers I have had lately dont lift their game I might have to take a serious look at that option.
Sorry, I didn't describe my problem very well I think..
By 180° tri y I meant that for a usual firing order of e.g.13726548 you can pair
23 primary collector
with in secondary collector
58 primary collector
and
14 primary collector
with in secondary collector
67 primary collector,
which would give 180°/720° in the primary collectors but in primary AND secondary it would give 180/180/180/180. Sorry if I gave it the wrong name.
Can anybody of you tell if that will change the engines noise (I presume it does, as Russ wrote above)?
thx
By 180° tri y I meant that for a usual firing order of e.g.13726548 you can pair
23 primary collector
with in secondary collector
58 primary collector
and
14 primary collector
with in secondary collector
67 primary collector,
which would give 180°/720° in the primary collectors but in primary AND secondary it would give 180/180/180/180. Sorry if I gave it the wrong name.
Can anybody of you tell if that will change the engines noise (I presume it does, as Russ wrote above)?
thx
Let me get this straight, are you saying you are going to merge the secondaries for 2/3 and 5/8 into the one collector? And 1/4 and 6/7 into the other? That's an interesting setup!
Is the idea to merge the secondaries across the back of the motor as with a normal GT40 crossover system but of course needing to find space for only four pipes not eight?
Is the idea to merge the secondaries across the back of the motor as with a normal GT40 crossover system but of course needing to find space for only four pipes not eight?
Should work OK, will be slightly better than a tri-y setup where they are kept bank for bank, may even build a bit more mid range torque on street application. Wont sound quite as even as 180° 4 into 1. Has been used before in circle track application with 180° type where rather than connect the 4 pipes into each collector as one they split thru two merge collectors before combining into each tailpipe- this was done to try and build some mid-range power and used as a tuning tool for different tracks. Have also seen setups where they run 4 tailpipes, this has a very distinctive ' multiple Harley type ' sound.
Russ and JacMac, thanks.
Right, Russ, that would be the benefit of this layout - you woudn't have to go straight cross the induction system or something else like that and you would save a lot of space in the rear. But I think the pictures of the headers of Mike Trusty in this thread at page 1 are absoluteley the same thing I am talking about.
Right, Russ, that would be the benefit of this layout - you woudn't have to go straight cross the induction system or something else like that and you would save a lot of space in the rear. But I think the pictures of the headers of Mike Trusty in this thread at page 1 are absoluteley the same thing I am talking about.
Duh.. Old timers disease! I'd forgotten about the pipes in that photo. Only a year ago too!
Hi Jac
need to resurect this older thread, because i checked on my exhaust system in regard to my firing order and got confused.
Again
Your answer was based on the two pics above. By checking again i think although it is the correct pairing in both colletctors and the right side also has the correct rotation order, the left side is not following the recommanded rotation order. Adams system is like this
6--1
7--4
This way it is "ZETTING" instead of rotating.
So either 1 or 4 need to exchange incoming positions in the collector or 6 and 7 to achieve also the correct rotation order.
Or is there any other reason why it is built that way ?
Thanks for your help
TOM
