EpitrochoidalPower!

hmmm. Its not as close as it looks but i'll have another look tomorrow and see.

Templeton

iTrader: (10)

when are you planning on another dyno run? im very much considering doing an n/a b/p, but i dont think 200 flat will do it for me how much power do you think is left to be squeezed out of it?

EpitrochoidalPower!

Its still going to be a while. Don't have the money to do the header right now, waiting for end of this month or perhaps the next. Must still finish up tuning as well. My stepfather had to borrow my laptop so I'm stuck at the moment. Still running very rich on the top end. Another thing I need to tune is my acceleration enrichment, it is WAY out. It seems to be giving way too much fuel when I apply sudden WOT and the engine hesitates momentarily before spitting the excess fuel out and getting on its way. My timing is also quite conservative at 20 degrees max advance and as I said header and resonator are far from ideal. I know how important a good exhaust system is on a bridgeport so i'm confident that will free up a few ponies once I get it done. My ports are about as big as one can get without cutting into the water jacket (J-port) so i'm sure they are good for more power. As I said ive improved the intake manifold and I think my airfilters were compressing at high rpm and restricting flow so perhaps my new cone filters will help aswell. I don't want to throw outrageous figures around but when I consider how many improvements I can still make i'm fairly confident I can hit 210 - 230whp. If you look at SCCA RX7 RACER hes making 196WHP on a street port. It shows what finding the perfect tune, timing and setup can do. I'll keep working at it until I know i've squeezed everything out of it.

Rx7_Nut13B

iTrader: (1)

You are loosing alot of power in your timing, bridgeports like alot of advance, 20ish is on the low side, on a NA I would be looking in the 30 range with a good 10 split.

On fuel you should be shooting for 12.5-13.0

A full BP 13B with open exhuast running a carb should put out about 300hp at the flywheel so you have alot more power in there

EpitrochoidalPower!

Yes thats what I was thinking. I cut the current header off today and also the resonator and I was right the inner tube had broken off and wasnt aligned anymore. I'm sure that must have been restricting flow a lot. I have almost finished tack welding my new header up. Its turning out very nicely will post pics soon. Will replace that broken resonator with 3 inch tubing as well. Once thats all done I will start advancing the timing and see how it goes.

dj55b

iTrader: (2)

You should post up pictures of the headers you're welding up. What sizes are you going for?

As for the Acceleration issue ... like I said you'll most likely have to run it on 2 maps to get it going properly like I did. I was having the same issue of the accel enrichments would either go on too easily and almost stumbling the engine while cruising or idling, or I would get a second of lean spot then it kicks. But with having a dual map setup you're barely adding any accel for an economy map ... I think the highest that I have is like 3 or 4 ms ... because the secondary map takes care of it. My race map is a little different ... and my accel just to prevent any detonation or anything like that i think my max setting is set at about 8ms at WOT.

You should take it out to the drag strip and see what you do... I was there yesterday and did a 14.6 ... my buddy with a 1st gen with a S5 T2 street ported did a best of 14.3 and thats still me having issues hooking up properly first gear ... and third gear in his tranny is better than mine First and second I'm neck and neck third he starts pulling .... Also me against a mustang with a v8 i was faster to 330 ft ... but he started pullling on me after i go into third.

EpitrochoidalPower!

Exhaust manifold almost done, lengths are matched, ID of about 1.9" mandrel bent, thousand times better than old manifold, will put it on soon, think i may have to remove steering box to get it in, right hand driver car.

EpitrochoidalPower!

Some more pics. I have also included some pics of the remains of the old header and resonator/pre silencer. As you can see, header was far from adequate and resonator is screwed.

Jimbo II

I may of missed if you are already, but why don't you run twin pipes joining at the diff? I always thought that was the ideal setup for a rotary?

To keep the exhausts from the rotors seperate for as long as possible...

EpitrochoidalPower!

It seems that it generally the case for stock and streetported motors. However when it comes to bridgeports and peripheral ports it seems its better to go for a short header collecting into a 3" or 4" exhaust. This is what i've found from researching on the web so it may not be true but ive seen a few threads where people have said do not use long primaries (ie collecting at diff).

Here is one such thread:

https://www.rx7club.com/showthread.p...geport+exhaust

dj55b

iTrader: (2)

Are you sure thats Mandrel Bent tubing .... because that looks pretty rippled to me. This is a good site with decent prices for mandrel bent piping. Note how different they look:

http://store.racing-solutions.org/180deu.html

EpitrochoidalPower!

Yes im sure. Its only the one bend thats rippled like that and I felt inside and its smooth on the inside. Perhaps the machine wasnt lubricated or setup perfectly for that bend but you can see the marks from the mandrel inside the tubing so I know it was mandrel bent. If you look on the racing beat site you can see that there is slight rippling in their mild steel mandrel bends. It may have something to do with the stiffness of mild steel vs stainless steel as racing beat uses mild steel whereas the site you posted was stainless. Its not prefect but im happy with it because the pipe diameter is the same in the bends as with the straight tubing whereas with normal bending the diameter decreases ALOT through the bend. Bends also cost me next to nothing. Spent $28 on having all my bends done including the cost of the actual tubing. Also with the current economic state of things its far too expensive for me to order anything from the US.

Heres a pic of a mandrel bend from the racing beat site, you can clearly see the same ripples, im not saying its supposed to be like that just seems ripples can occur on a mandrel bender:

dj55b

iTrader: (2)

weird ... I've dealt with both Stainless and Mild Steel mandrel bends before and they were both smooth on the outside ... Just looked up quickly how they do it on a mandrel bender:



I guess if those things aren't spaced in together properly they could create that look on the outside.

EpitrochoidalPower!

Yeah must be something in the quality of the machine or the way they set it up. I'm looking around for a new pre-silencer now. I could just run a section of 3" tubing but that might be a bit too loud. Got a hold of my engine builder and he recommended a place which I will go check out tomorrow. He says I should be able to get a megaphone there too. I'm also going to wrap my header to keep more of the heat in as the wall thickness isnt too high, may even help to make it a bit quieter too.

dj55b

iTrader: (2)

How does the inside of that collector look like? As for presilencer you could just do like me:

https://www.rx7club.com/showthread.p...hlight=muffler

EpitrochoidalPower!

Not great inside...very basic as collectors go. So im going to see if I can get a different one today from this exhaust place. If I cant then ill look into making myself a proper merge collecter.

dj55b

iTrader: (2)

If you can't find anything, shoot me a PM and I can probably TIG weld one for you for the price of the pipe and shipping. Shouldn't be that much. I designed and built he headers for my local University's Formula SAE car and gained about 7whp ... for a car that only makes 74 whp .. thats quite a bit . here's a shot of it in mid construction:



A bit more into it:



On the dyno:



The Car:



If I recall correctly, I did the collector at 13.5 Degrees from the centerline. I'll have to dig out my jig and see.

Jimbo II

Oh ok, I thought running twins to the diff stopped the pulses generated by the rotors(especially in ported motors) from interfering with each other and disturbing exhaust flow.

EpitrochoidalPower!

Thanks for the offer dj55b but i'll see how things go this side for now. Looks like a nice header you made there, and a nice little car . Im struggling to find a megaphone, I found a place that might be able to do it but must still make sure. It only needs to go from ~2.4" to 3" so the taper isnt too high. The same place can make me up a new resonator for a good price must just check what they use as packing to make sure it will stand up to a rotary.

karism

Ok,lets have a look at the header.

It is difficult to judge by the photo.It looks like the length of the header is quite long?What is the lenght of the pipe from flange to collector entry?

It you look at the lenghts that racingbeat recommends :

Short system : 13-15 inch
Long system : 113 -118 inch

The angle of the collector is also very,very important. Iam running a 15deg angle on my beetle,that the gas combined gradually (sp?).

It is also best to put a devider where the pipes join,to prevent reversion of the pulses.

Karis

EpitrochoidalPower!

Yeah it is a bit longer than I would like but still much shorter than my old header. Its about 30", the racing beat site recommends around 24" for Bridgeports on a weber IDA so considering im using weber style ITB's and intake manifold I aimed for that. Problem was its difficult to get the primaries equal length without the bends being very tight. When I have some more time and money I will try experiment with different sizes. For now im sure i'll see an improvement solely due to the fact that they are mandrel bent, equal length and larger diameter. Replacing the shot resonator should help a lot too. Gave myself a nasty cut on my finger today with the grinder, was rather silly accident, doctor wouldnt give me stitches though because the cut wasnt clean, but its not stopping me from finishing up this welding. I have to remove the steering box to get the header in, i'm not looking forward to that, it doesnt look like a nice job. My other idea was to undo the engine mounts and jack the engine up to get some clearance.

EpitrochoidalPower!

Also, racing beat recommends 30 - 40' angle for the collecter. Mines between 20 and 30 so far as a know. Thanks for the input, ill get the car back on the road ASAP and back on the dyno.

RotaryPicha

iTrader: (2)

Hows are doing milage in the city? highwy you said bout 30. I might be gettn in two weeks TweakIt ITB's and a megasquirt ecu off somebody on this Forum. I know you have to tune it for better mileage and switch for more horsepower just wanted to get an idea where I could be when im drivin around. Thanks

Whould love to see some videos of your car at Idle, cruising and flooring it. haha

Templeton

iTrader: (10)

update?

dj55b

iTrader: (2)

I get about 30mpg as he does on the highway ... on the street i can get about 17mpg. I'm sure i could tune it more and save a more gas and not give it atleast once a day. So maybe 19-20 .... not too bad.