Exhaust back pressure

[boyan]

Hi guys

Hope you all well and good and still torquing !
Has been a bit of time since my last visit but been busy working on cars and holidaying
I'm having a little isue with my exaust back pressure so i just wondered for anybodies honest opinion!
Yes two years later and im still tuning my jaguar xjr sport N/A 4.0 auto! got the engine done pretty well
after all that hard work i did port and polish port match and so on but i got the problem with the back exhaust pressure...i opened the exhaust to much so it flays above 2000 rpm . but under that just woooo wooooo and i have been fighting now with this for some time ...if i mount everything back together the original down pipe and mid section silencers and so on i lose on top end witch i don't like at all ...
so i came up with the little solution in the end as the engine is in-line 6 cylinder 24v and i opened the
exhaust back pressure points to full throttle i lost all the torque at low rpm ... so i figured out if i joined the two down pipes with the H pipe right before the down pipe joins in two...i will get some back pressure with out effecting the revs trough the range! the result is amazing i got what i was looking for i also increased mpg to my surprise engine sounds really nice and quiet but only one thing bothers me wont this idea burn my head gasket if i created to much back pressure ?

thanks
boyan

 

[obi_waynne]

Hey buddy, good to hear from you again. Sounds like you've been having a blast.

Things are going well here, we have a new forum which I hope you like. It's much faster and easier to use than the old one.

I like your thinking there. I think your gasket should be fine, is the engine running much hotter then?

 

[boyan]

Great forum Waynne yes i do admire this forum and is great in every way ! bit more for the big boys but i swim along!
Yes the ides is great solution i think ..no not running hot at all but i rather ask than be sorry ! i put to much work in to that engine need few final tunings and ill be done

 

[obi_waynne]

Glad you like the forum, we are all learning along the way.

 

[bax]

Welcome back and congrats on solving the problem

Waynne id like to know more about Back pressure and exhaust systems since im planing on installing bigger exhaust , am i going to have the same problem with back pressure at low end with my 2.7 Diesel ?

 

[obi_waynne]

Diesel engines are very different to petrol engine, most standard exhaust sizes on diesels are quite large anyway. Are you hoping for a power gain from a bigger exhaust on the diesel, of so I think you'll be disappointed.

 

[bax]

im hoping for a little bit of power gain ... like 5HP or so .. or is that too much to gain from such a mod ?