GROUP BUY BTB tubular manifold

So just to clarify.

Is the car being dyno tuned on the RR using the std exhaust and then being retuned using the new exhaust.

Karl

>I've learnt in years of tuning is that unless you follow a logical >sequence and plan properly you never know which of bits you have >bought or made actually make you go faster so you just contine to >spend hard earned money on items that look good but give poor >value for money

you have a good point there.  what you are criticising is that "bolt on mentality" generally only takes you so far.  You will never get the big gains. The reason is that what often is done by changing a larger exhaust header with more flow potential and resonance at higher rpms, or larger intake manifold, etc.  is that all you do is change the breathing potential of the engine. But there is nothing inside the engine to back that up. So the potential is not taken advantage of and you dont get the power gain you hoped for.  If you havent made too wild a change, then what usually happens is that you somehow change the power deliver curve.  Peak torque may move somewhat further up the band -- which is good for a track motor.  But, usually, unless you have a FULL ENGINE CONCEPT worked out, you wont get any eye-brow raising. HP really does not add up like people expect it to.   These are already quite fine tuned and efficient engines from the factory.  Now if you were talking about old Chevy motors where they had major restrictions on the engine (cheaply built mass produced engines), then anything you do to those engines basically increases power -- up to a point.  Once you approach the true efficiency of the engine, its becomes the same as with S14s -- it takes matched engine components to squeeze out the power.  But, they have plenty of products available to do that, just look into the racing or drag racing scene and you will find all sorts of stuff.

Im not surprised the header does not do too much on a stock s14, because the stock header has been proven to be very efficient over its working band of 1000-7000 rpm.  The only real flow restriction in the stock exhaust system is a catylitic converter.  BMW did do their homework.  I also know from swapping exhaust systems on my own engine, that a retune is necessary. You should have a semi-optimal tune for each exhaust sytem, then dyno each on individually.

On higher output S14s,  I also know that the stock exhaust system is a restriction, and I also am pretty sure the single pipe exhaust setups are as well, atleast the ones up to 3" diameter, not a large restriction, but also not as good as a dual 60 mm pipe setup in the midrange and topend area.  Going with larger pipes though tends to increase the level of a secondary resonance down around 2500-2800 rpm and can cause a torque dip around 3000-3500 rpm. So there are trade offs here.  A dual 50 mm or dual 55 mm pipe might be better here.  I dont think any of this makes a difference though until youre running around 280+ hp.  In this arena, and given we usually have power band in the 5000-8000 or 6000-9000 rpm area, then the headers above could paint an entirely different picture. We wont know unless we just try it out, they look promising to me.

I dont know what the merges are going to do. I think that they will approximately do what a 4-1 header will do, because the merge is in the same general location.  It might make the header a bit peakier and biased toward maximum power in the powerband, this makes it make power in a narrower band though. This is just pure speculation on my part though. That is mostly how a 4-1 header behaves vs. a 4-2 header. Ive not scene any dyno plots and I may be quite wrong.

John

Nick @ TBMW wrote: Well, it looks like the car is being tuned either today or early next week, so hopefully we should have 'something' interesting that you can look at.

Has this happened yet?

Also as asked earlier is the car being tuned on the 'old' exhaust first and then 'retuned' on the new or are they just going for the latter to get 'maximum' gains..

I would be interested but with the lack of answers to some vital questions itmakes me wonder if my engine will actually benefit from this upgrade.

karl

Nick @ TBMW wrote: It was tuned on the new manifold (or do you mean exhaust?) which netted 175whp with the new cams in, so I'm afraid I can't give you a comparison of the standard and new item. Only way to really do it properly would be to get all four BMW manifolds and the BTB one and rolling road/tune for each. Obviously you're looking at a huge amount of hours and a huge amount of cost involved in such a task!

So we have no idea what extra power was gained by fitting this new manifold and what was gained by fitting the new cams.

Yes the project will take alot of hours and lots of money but for a logical well thought out article in a magazine that was writing about cheap upgrades then gains from each component in the build would have been useful.

It is quite possible the manifold is a complete waste of money.

Just my thoughts since I have just gone through a major engine rebuild but had it all planned out for me by John-M3.

Karl