I am just wondering the pro/cons of a header mod (pre-cat restriction delete) vs a new header. I remember reading that the header mod gains about 10ft-lbs across the board. How does this compare to for RMW, Mynes, or janspeed torque curve shape wise? I am all about bang for the buck. Any input would be appreciated. -Jonathan
This is a stretch, but the only con may be a slight decrease in mileage if you spend much time idling at the first start of the day. When you first start the vehicle it uses an enriched fuel map, once warm it uses feedback from the O2 sensor to balance the air/fuel mixture, under demanding load it reverts to maps again. The pre-cat accelerates heating of the O2 sensor, which triggers the change to lambda operation. However, no change in mileage for me. I've not seen gains of that magnitude. I have seen dyno graphs where an OE pre-cat delete header made half the gains of a tuned header on different configured MINIs. Not one of the headers you mentioned, but the spread was greater and growing above 6500 rpm for the tuned header. The biggy pro is low noise; a little increase in performance without a big increase in noise level.
If you frequent the Eu boards ( Germany/ England) they remove the cat and run the OEM Header.. Like Pictured above.. They seem to like it, as the Autobahn ( Germany) can be a pretty quick Place. The Janspeed is the manifold of choice in the UK. There is a drag racing group in the UK ( just another way to show power...) and they have run a bunch of dynos with Header changes.. Cost for the dollar, and not being a full time racer and not needing the gain above 6500 revs... Keith looks like the future!! Just me..................................... Thumper PS: Noise?? the quality and the thickness of the pipe in todays header usually will not allow any more noise from the header than the stock unit!! If there is NOISE it us a leaking system. Noise will be a better exhaust note, as any removal of restriction will over come the mufflers ability to keep the same exhaust note!! Tpr.
what are the gains does the header mod see over stock? gains of a proper manifold over the mod? -Jonathan
Sorry, can't provide hard & fast numbers. On two highly modified MINIs, one fluctuated gains 4-8 each on various pulls over stock, and the custom header made 10-14 hp over stock. Several MINIs in Germany made over 240 hp with pre-cat delete OE headers, so it didn't hold them back much. Below is the custom header dynoed at 10-14 hp over stock. It was a purpose built race component with large diameter equal length primaries, secondaries, plus well engineered collector.
i think this will be my next mod if i can get it done for a reasonable cost. bang for the buck seems like it could be good. thanks for all the info. -Jonathan
You probably would make power with the pre-cat delete, but I doubt you'd see 10 or more sustained ft/lbs. Those are the kind of numbers we would expect to see with a good aftermarket header which typically have better collectors than the stock piece.
and you know you can't post stuff without some proof....... this place needed someone to put some reality back into it talk is cheap:devil:
Not everybody has unlimited access to Dynos. I am waiting the day that one asks for Dyno data on the latest sub woofer system they install in their car. LOL Kieth does not use an engine Dyno which would be the best way to get accurate data. The simple mod works if a even a little simply be application theory of air flow and thermal dynamic principles. Gosh.................. stop with all the dyno requests! to quote one a reputable source : "What are the primary factors affecting chassis-dyno test accuracy? Do they vary depending on the type of dyno used? There are two ways to look at accuracy: accuracy of the dyno itself, and the effects of introducing other variables outside the measurement system that can affect what the car is actually doing. As long as the dyno is properly used and calibrated, then all dynos are accurate for the conditions. The pitfall is trying to compare results across different platforms. " What this means in a nut shell as an example: if you have a car on a chassis Dyno and you are not getting the numbers you want you can ice the intercooler and blow more air over the engine during the test. Hence "then all dynos are accurate for the conditions" I can supply anyone with the biggest in the Dyno manufactures in the business if anyone would like to learn more about the limitation of chassis Dynos? I would be happy to pm the information and a few good people to talk to.
I must admit................that last post is rich...............considering you have never dyno'd your car yet make plenty of claims
Tell us what is not real here, and provide support for your contention. Do you think, or can prove with a dyno plot, a pre-cat delete modification is not capable of producing the minimum of 4hp or torque? I'll be the first to say the 8hp outcome on one pull was more likely extraordinary and not indicative of the average potential of a modified OEM header, but it was one data point to report. Do you think, or can prove with a dyno plot, the custom header I showed a photo of earlier is not capable of producing at least 10hp over the stock header on a stock head? I have no dog in this fight. The dyno examples I have are not of my modified OEM header or a custom header owned in the past.
we weren't talking of the precat header we were talking of the header picture you posted I realise this proof on the internet is a touchy subject but having dyno's hundreds and hundreds of Mini's. I have a very good clue what's going on when I see the dynos footnote***** No jedi mind tricks were used in this post:arf: