UEL vs EL and Longterm Use

[Circuit Motorsports]

Overall, on the FR-S/BRZ/GT86 my experience has shown the EL header making a bit more torque/power in the mid and upper RPM ranges over the UEL, with a little less torque in the lower RPM range (some EL header have not exhibited this in the lower RPM range). The amount of gain the EL provides is dependent on many factors -- it is not a tremendous amount, but in N/A form every little bit helps.

Stick to a high quality header, choose your sound preference and powerband, and you'll have a win, as any well designed EL and UEL header will net you decent gains and with a tune will eliminate the torque dip.

I quickly grabbed a couple graphs from my laptop for comparison, not the best graphs, but I think they make the point. Different cars, different days, same dyno. For this comparison, don't compare the numbers, just the shape of the graphs. Both graphs are after tuning:


EL header, with tune:



UEL Header, with tune:


As you can see, both have very linear power curves, and very flat torque curves, with no torque dip. Both performed very well. Look at the shape of the torque curves, and you will see the EL header producing a small increase in torque through the mid-upper range (slight up-hill, vs. the flatter UEL torque curve).

- Bob

[skyloran]

Originally Posted by Circuit Motorsports

Overall, on the FR-S/BRZ/GT86 my experience has shown the EL header making a bit more torque/power in the mid and upper RPM ranges over the UEL, with a little less torque in the lower RPM range (some EL header have not exhibited this in the lower RPM range). The amount of gain the EL provides is dependent on many factors -- it is not a tremendous amount, but in N/A form every little bit helps.

Stick to a high quality header, choose your sound preference and powerband, and you'll have a win, as any well designed EL and UEL header will net you decent gains and with a tune will eliminate the torque dip.

I quickly grabbed a couple graphs from my laptop for comparison, not the best graphs, but I think they make the point. Different cars, different days, same dyno. For this comparison, don't compare the numbers, just the shape of the graphs. Both graphs are after tuning:


EL header, with tune:



UEL Header, with tune:


As you can see, both have very linear power curves, and very flat torque curves, with no torque dip. Both performed very well. Look at the shape of the torque curves, and you will see the EL header producing a small increase in torque through the mid-upper range (slight up-hill, vs. the flatter UEL torque curve).

- Bob

Nice write up, can you get any data from a Tomei EL vs Tomei UEL header? debating which one should i order.

[akahenry]

Originally Posted by skyloran

Nice write up, can you get any data from a Tomei EL vs Tomei UEL header? debating which one should i order.

dude just get the UEL because rumble. I ordered mine 5 days ago and will be getting mine in about two weeks time.

[mokinbird87]

I had my bugeye with stock UEL header for 200k miles. zero problems.

[Circuit Motorsports]

Thanks! Haven't tuned the Tomei headers yet. Once I do, I'll be sure to post up the results.

- Bob

Originally Posted by skyloran

Nice write up, can you get any data from a Tomei EL vs Tomei UEL header? debating which one should i order.

[hahaman86]

I'm glad this thread got revived I'm very curious about the sustainability of the engine with an EL or UEL header upgrade in the long run as I am in the market for a set right now. Thanks! Subbed for updates

[stonenewt]

Originally Posted by moto-mike

Misconception is that an equal length is the only one that does scavenging. In reality, the equal length simply does scavenging better.

To paraphrase the entire chapters on exhaust manifold tuning from 2 different books on this subject -

The manifold design will be down to the design parameters & engine bay constraints. Properly tuned equal length runners will produce very effective scavenging in tight rpm bands. However, EL manifolds while have bands of conflicting flow causing dips in the torque curve. Unequal length manifolds each runner fall in & out of harmonic sync with the other runners but not at the same time. When the length of each runner is tuned properly this will cause less efficient scavenging but over a much wider rpm band. A lot of supposed deficiencies of UEL manifolds are because they are harder to tune correctly as the length of one runner effects the optimal length of the other runners.

Yes that's going to be generalised & wrong in certain respects as that's about 85 pages into 1 paragraph.