TwinCharged RX7

iTrader: (14)

I have just installed a rebuilt, streetported engine in my 94 FD, it has a Greddy T78 single, full 3" exhaust, and TEC-3 GT ems and ignition system.

The TEC-3 was tuned for the old stock port engine. now that i have a street port, something is not quite right. I guess it could be something that i have done wrong during the install, but i really think i have it hooked up right.

The Problem:
below 3k rpm, there is almost 0 power, i have to downshift to second and still barely make it up small hills. at 3k rpm i hit positive boost pressure and the whole tone of the car changes and i have power, and i don't go over 4k rpm b/c im on the break in period. Its almost like a piston engine not firing on all cylinders when i'm below 3k rpm, and then all of a sudden kicking in. it also back fires like crazy when it drops from above 3k rpm to below 3k rpm, like shockingly loud, not just the normal burp. i think either my timing is off or i'm getting too much fuel at the low rpms.

Does anyone know where i should start with adjusting the tune? what do you need from me in order to recommend something? i dont have a wideband yet, but when i get one that will help, but any experience on going from a single turbo stock port to a street port? what adjustments would u expect to have to make based just on that?

I'm scared to drive it any more b/c the backfires are so loud and its just not right, i don't want to wreck a new engine.

rx72c

iTrader: (8)

how big was the street port?
if anything id say it is lean, BUT if your afrs are good and its still being gutless it would be something in your porting, in general porting does remove some low end ***** but it should be as much as you have described.
I would richen up your cruise area and low rpm up to 4000rpm by around 5-6% and see if it helps.

TwinCharged RX7

iTrader: (14)

thanks for the reply, thats what i was thinking at first too, street port means more flow, which is more air, i still have the same fuel maps, so you would think i'd be leaner than on the stock port.

but what about velocity, since when i'm not boosting and im at the normal vacum levels , under 3k rpm, could the slower air flow be causing my fuel not to atomise as well? assuming that the street port creates a slower flow at low rpm's since the volume is greater but pressure is the same. not even sure this is true or not, just a thought.

It just seems rich to me which is why i thought of the above. no power, and once i hit 3k rpm the whole tone changes and its like its miss firing until then, either the timing isnt right and one of the plugs isn't doing its job until it kicks in like someone hit a button at 3k rpm, or its just getting too much for the plugs to handle. and at the high pressure (above 0 psi) it combusts by itself or the spark is stronger, or the map just leans out a bit there. and when i let off after 3k rpm and let the engine slow the car down, i get huge backfires, unlike what i used to see, shockingly loud. which would point to too much fuel again.

anyway, i'm fixing the oil pan, tomorrow night and then i'll get a lap top hooked to the TEC3 so i can post some more detailed info. please keep any other ideas coming.

2Lucky2tha7

iTrader: (3)

You're shooting in the dark right now. Buy a wideband and don't "guess tune" at the expense of your engine.

ivegonemad

i would say its unsafe(not recommened) to give boost to a rebuilt
engine you should break it in on no boost, after 1k mile i would start intorducing boost however i would just re-tune the whole car, a stock port has different timing map and fuel maps so you'll just need a re-tune...IMO

ivegonemad

+1 can never go without a wideband!

TwinCharged RX7

iTrader: (14)

yeah, i am trying to find either an aem or innovative, hopefully i can get it on its way tomorrow.

and i'm not really boosting, i cant help it if i hit a few psi over 0, i've got the boost controller off, and the wastegate is 9psi, so i have to be careful not to get anywhere near that

TwinCharged RX7

iTrader: (14)

and thanks for the comments, i'll let everyone know when i get the wideband in, good thing my down pipe already has two bungs in it.

ivegonemad

well ill just try to stay away from boost, im just following what racingbeat has said and from what my builders/tuners have told me...

TwinCharged RX7

iTrader: (14)

my innovative wideband came in today LC-1 with an XD-16 gauge, it was used, and the sensor has carbon residue on it, should i clean this or let it be? And if i should clean it, do i just spray it with break clean? or should i use mass airflow cleaner

arghx

iTrader: (3)

this thread is useless without accurate datalogs

rx72c

iTrader: (8)

I build many engines for race cars that are built. Tuned to full power. And raced with no break in period.

Only time i suggest a break in period is with New bearings or shaft.

Other then that. Seals will take ages to bed in and 1000kms wont do much in that respect.
If an engine is clearenced correctly, and uses quality parts. Engine break-in is a myth.

kenn_chan

sound like a problem I saw on a car built here locally, the owner while swapping motors "bent" the front of the journal shaft.

I am not sure how he bent it, either by bouncing it on the front braces while installing it, or by overtightening the a/c or P/S belts. Hell he might have done it with a jack, I saw him jacking of of the front of the engine (I assumed it was the oil pan, but he could have been pushing off of the crank) to lift the engine slightly to make the tranny line up easier.

but regardless he bent the journal shaft and when he could get it to start it ran for **** below 3 K or so, and then once it got going fast enough it would run fine.

ended up the ignition was wonky below 3K because the pick ups for the crank sensor were not reading for **** below 3K due to the shaft being slightly bent; (you could see it wobble at below 3K RPM's) once it revved above 3K it appeared that the wobble was fixed. my first thought was he had not tighted down his pulley on the front. but when we checked it was tight and not loose in any fashion.

it was fixed by rebuilding the entire engine as the journal shaft was fubar.

kenn

rx72c

iTrader: (8)

Im not sure about that.

IT IS POSSIBLE...?

BUT.

I have seen engines come out of cars with huge front end accidents where the pulley has been hit very hard and not bent the shaft. but hey anything is possible.

TwinCharged RX7

iTrader: (14)

yikes, i hope its not that. i didn't jack on the the engine at all and i was actually worried about the belts being not tight enough, so i dont think those have bent anything.

The wideband is installed, i just need to get a stereo cable so i can plug the LC-1 into the XD-16 guage. I guess thats what u get for buying used. Anyway, i finished the oil pan reseal on saturday night, so it should be fully cured now and i'll be able to start it tonight and see what the afr is. then we can get down to business, thanks again for the comments

2Lucky2tha7

iTrader: (3)

The LC-1 with the XD-16 gauge is an excellent setup. I would bet that the wideband sensor is fine, just make sure you do the free air and heater calibrations and you should be fine.

TwinCharged RX7

iTrader: (14)

Ok, oil pan is not leaking, and wideband is calibrated.

I got the car to idle by itself once it finally got warm. right now it will idle in neutral without the clutch depressed at right about 1,750 rpm. i've had it idling at 1500 once its fully warm but can't go much below that for some reason.

My AFR was all over the place during warm up, but once i was able to stop playing with the gas and it was warm idling around 1700 rpm the AFR was steady between 17 and 18. and sometimes would slowly creep up higher than that by itself.

It definitely does not sound quite right, occasionally it will burp a few times and the tone i expect becomes audible for a second, then it goes back to sounding strange. hard to describe but i would say a "lighter" tone, like not completely combusting or something. I get huge back fires once in a while if i touch the gas and then let it return to idle.

Any thoughts?

2Lucky2tha7

iTrader: (3)

lol, how is it even running at 17 or 18 afr at "idle"? For starters, you need it around 850 rpms and 13afr at idle...........or you have a huge vacuum leak!

TwinCharged RX7

iTrader: (14)

yeah, its not good. the break in guide at rotaryresurrection.com says that it won't run right for a little while and you gradually bring the idle donw from 2k, then to 1500, and keep drecreasing until it runs right. i think i'm now past the point where i should be normal.

vacuum is -19 psi pretty steady when its "idling" now. If i have a vacuum leak i'm not really sure where it could be, there aren't many hoses left b/c i have just the single T78 set up. when i have driven it (20 miles) boost will build.

could the primary injectors be messed up? the reason i dont think so is that if i give it some gas it will perk up pretty quickly

not sure if this helps, i plan on spending a little time with pf supercars on the phone and the laptop hooked up to the tec-3 tomorrow, but please keep comments coming. i'd really like to be able to drive it haha

2Lucky2tha7

iTrader: (3)

did you mechanically adjust the idle yourself via the idle screw, or it just so happens to be idling that high?
If you have no vacuum leaks, then by all means add more fuel because 17 to 18 afr is too lean and is something you only tune for while cruising in vacuum. During break-in, I keep it around 13 afr wherever the idle is set at, and then I keep it around 15 afr during cruising in vacuum, 13.0 afr at 0 vacuum/boost and then it tapers down to 11.5 after that, but I won't get into those specifics yet because you're not supposed to be "boosting" it yet.

You are currently running too lean.
Period.

P.S.: try lowering the idle and get it down around 1k rpms and see if it's still really lean. If not, and it's around 13afr or so, well then it was running really lean around 2k rpms because that's what it must have been tuned for during cruise at that rpm.

TwinCharged RX7

iTrader: (14)

i have the idle screw set to have it idle that high currently. if the idle drops below 1500 it starts to sputter out.

thanks for the info on the afr. I really hope after i run the tec-3 diagnostic that it tells me something just isnt hooked up haha, but i really don't know what it could be.

whats your thought on going from the stock port to the street port and leaving the tune the same, why would it be so lean now. (other than me hooking something up wrong)

kenn_chan

For what type of car?

for a rotary, very, very possible.... look at the depth of the threads in the front of the journal shaft. Now look at the assembled depth of the front pulley, the threaded section ends at the same depth as the pully, and the wall of the shaft is very thin, overtightening of the belts can bend it let alone what you could do with a wooden block and a jack, hell who knows but it is possible.

kenn

killahrx7

i've never seen a tec-3 fuel map or set up, but it sounds as if there's a problem with your primary injectors cause only when boost comes on the car runs good which could mean that only your secondary injectors are working. try swapping injectors and see how the car runs. just a thought as i'm no guru

2a+RoN

Why are you asking all these questions when using the stock port tune on a new streetport? The new setup needs to be tuned. Get the motor tuned and then see what problems arise if any...

Dudemaaanownsanrx7

iTrader: (23)

i agree. 17 + afr is too lean. It will stumble and and buck. you might be able to tune it to about 16.5 under cruise at 70 mph. But for now i would try to get it to at least 13.5 - 14: under all vacuum conditions. start rich then lean it out to where it likes it.

Under low boost don't be higher then 12:1. you should not be boosting the car at all yet though. at moderate boost dont be higher then around 11.5:1