It's a S4 TII conversion.

I have a walbro and cleaned and tested 550's.
Racing beat dp and silencer to Corksport single.
Rtek V1.5 ECU(3500 rpmsecondaries,FCD removal,timing retard over 9psi)

It runs relative stock boost right now because I haven't put a boost controller on it yet.

I run 5-7psi in 1st/2nd
then 7-9psi in 3rd/4th/5th

Well,
The car will do little surges/bucks like a hesitation when I get on the throttle.
It usually does it in the low/mid range rpms.

I'm kind of guessing it's the AFR's.
My FPR is getting killed by the walbro and I push 50psi as a base line pressure.

At idle I run 11 AFR's. It smokes quite a bit due to this.
Under boost it was around 12's I think. It was a while ago I got it checked.
Right at the secondary injector turn on it will go lean real quick and then jump back into the 12's.

So any thoughts? Would the extra pressue be causing the weird hesitation/surging?

 

Oh God, another 20 page thread from Digi, lol...

Well, she ran good for a while there, once you got all the bugs worked out, eh?

I thought you had a fuel pressure gauge on that bad boy? It seems to be the month for screwy FPR's, I must have started a trend, lol...

I found mine by watching the O2 sensor while driving, she just kept getting leaner & leaner while cruising, and I replaced the pump to no avail...Finally got the part in today, I'll put in on sooner or later...

In your case you might be shoving TOO MUCH fuel in, instead of not enough, but you'll never know until you get some AFR or O2 sensor readings...

Mine does that, too (goes lean right before the secondaries hop on board), on a basically stock ECU. After that she runs rich as hell, all the way to 125+ (when she's working right, lol...)

 

I thought that rtek chip was supposed to take that dip out when the secondaries kick in hense the secondaries comming on at 3500rpm instead of 3800??? Mine does the same thing, after I put the fmic on and wait a little while I am going to get a wide band and see how tuning it will effect these slight surges. Some people have said if you don't have the pellet inside your vac hose this may cause it, as a matter of fact I'm going to put mine in now.

 

Does it do it under ANY load, or only under boost.

 

really only under boost

 

under boost.

it cruises fine.

I have a fuel pressure gauge in there. I do 50-55psi constant.
I have an Aeromotive FPR in my house waiting to be put in.

I also got it on a wideband sensor.
I pulled 11afr's at idle.
I think I was in the 13's at cruise.
12's in boost. 5 or 10psi it was in the 12's.

At 3500 rpm secondary kick on it dipped to 14's
I haven't added extra grounds though so I figure that's a part of the problem.
I usually let off and do minimal boost at the kick on point to help prevent any bad situations.
I have even had times where the car jolts at the turn on point.


Oh yeah.
The rebuild has 4k miles on it so far.
The car can idle at 700 rpm but will eventually start to smoke big time.
It's vacuum at idle is 10(stock port ).

 

Wow...Why is your vac so low?

That's amazing that you're hitting AFR's of 14 with the pressures & injectors you're running...

What's the smoke at idle? Oil?

As far as the grounds, you KNOW that you have a good rear rotor housing ground by now, right, with all the stuff you've been through. Where is your main ground, down at the starter? And what is your alt voltage? (read from the battery posts while running)

 

yeah on my stock port jspec I'm getting 15-17 vacuum. I read a thread somewher that talked about a guy having this problem and he had an internal problem with the engine, hopefully thats not whats wrong with our cars, he had one of those rare cases. Anyways I see 55psi only when getting on it in the boost range but driving around normal I'll be in the 40's is this the same for you???

 

Could also be the TPS. Check that piece of crap. I've gone through a couple.

 

Well I will redo my ground but I know the EFI harness rear rotor housing ground is perfect.

The main ground is secure to the tranny/bellhousing/rear iron area

The vacuum has been really bad lately. I don't have any visable vac leaks and it idles at a constant rate(other than hearing some missing/assumed too much gas)

I haven't done a compression check after the rebuild breakin but last time at 1400 miles I only had 80psi cumulative and 65/70 on each rotor face.

 

With the talk of running lean directly after the secondaries come online, I found this dyno of a bone stock s4. Check out the air fuel ratio as it hugs 12:1 from just after 3800 to almost 5000. Before the transition, and especially afterwards the stock car does run stupid rich.

For additional comparison, check out my dyno sheet from about 18 months ago.
At the time the set up consisted off:

thunderfabrications 3'' dp/mp
apexi n1 single
TID
walbro
fcd
and mbc set to 11 pounds

The rpms are actually twice what they should be, so just divide the x axis by 2 to get the true value. It was during a mustang group dyno, and the monkeys there did good just finding ignition coils on a non-mustang car.

From 3800 to 5000, the car runs about 13:1 air fuel ratio until settling back down a comfortable mid 11 air/fuel ratio.

Imagestation sucks, and the pics are too large to upload via the rx7club server, so someone please host these. I don't have any program to resize the pictures on this computer.

edit: I'll try to upload my dyno again, it didn't work but here is the stock s4 dyno.

 

Well.
Last time I wide band tested. It turned out my wastegate line was non functional so my boost went as high as I pushed my foot to the floor.

At 5psi I pulled 12 afrs throughout the rpms except at the 3500rpm kick on where it went lean.
at 10psi I pulled 12 afrs throughout the rpms up until 6000-6500rpm where it went towards 14 and I let off.

I'll have to do a few tests.
One of a gradual sweeping of the pedal to the acuired boost and then one of full out mashing the pedal.

 

damn that is some low *** compression even for used rotor housings after 1400 miles huh??? Maybe not but I always thought that was low and also after 1400 miles your car should be broken in even if they are used rotor housings.

 

i had this exact same surging problem digi7ech. it was a TPS (though mine is series5) problem. it was at like 2.0 at idle and its supposed to be 1.0


if your TPS is out of whack it could eff your AFR's all up at all RPMs boost levels (seems to be your problem as well)

just some food for thought

 

TPS isn't even in the picture at WOT (unless it just happens to be crapping out at the point the plunger is all the way out).

If in doubt, read the sucker from the ECU while driving her. If it's bad, you'll see it there...

 

did I sound redundant in my last post, lol. I wrote the first part then went to watch a movie and then finished the post, oops. Wayne did you take a ride yet with the fpr?

 

Nope, quit hijacking, lol...

I'll take her to work tomorrow and post results on the original "mini-hesitation" thread I started a while back (back when I thought it might be the CAS).

Digi, are you reading these vac pressures off of a gauge? Where are you sampling the pressures from?

I'm getting the feeling you're going to try the new FPR to see if that helps, no?

 

lol ,sorry

 

Ok, I am having the same problem. 6-6.5k I get hesitation, but I also have a pulsing idle, so I am going to see about replacing the TPS.