wreckerx7

After a few years of lusting for EFI, it's finally done. I used the RB holley manifold and a 4 barrel EFI (4 injectors) throttle body from F.A.S.T., with Haltech Sprint RE management. I'd thought that staging the primary and secondary throttles would help with the torque curve (not unlike the RB Holley does) as the TB originally would open the secondaries proportionally to the primaries, after only a few degrees of primary opening. Great for V8 drag engines, I guess. Without staging, the little 12a (street ported) would have a momentary stumble when mashing the gas pedal, which couldn't be tuned out. Too much too soon, I think. It IS a big throttle body.
So a system was put together using a vacuum actuator controlled by a solenoid which in turn was fired by the Haltech. It took a couple days of fiddling to get it right, but the results speak for themselves. Before, RB Holley 465:

Before: RB Holley 465


And now:

Now: F.A.S.T. 4 barrel EFT TB and Haltech, staged secondaries


40% gain in HP, but more importantly, just look at that torque plateau! EFI for the clear and outstanding win.

I haven't driven the car myself, yet, but I'm told it is an 'entirely different animal' which has traction issues in first and second at full throttle. As well, 'rotating the car around corners with the throttle is easy now, in 1st ad 2nd', and 'it eats up the road when going through the gears'. Of course, these descriptions must be kept in the right perspective. It is, after all, a normally aspirated 12a in a world where youtube is sodden with videos of people getting rubber in 4th or 5th when boost hits.The point is, the dynamics of the car have been entirely changed and it has gone from being fun to drive to something much more than that. I can't wait to try it out myself in a few months when I get home from overseas work.

Here's the throttle staging in action. (It has since been adjusted so the secondaries open fully) :
click for video
As a side note, it is currently running premix. The plan is to set up the oiling system similar to a 13b, with injectors tapped into the manifold runners. After which, a lean ratio of premix will still be used as a cushion, but the majority of apex seal lubrication will come from the MOP.

Big time credit to Mike at Whitehead Performance ( link to whitehead performance ) for doing all the mechanical work on this car, and Radek at RStuning ( link to RStuning ) for putting together the staging system and tuning the EFI. Both these guys do awesome work and anyone can utilize their services with confidence.

I know that turbo engines are the 'go-to' for power these days. I have a well-sorted, turbocharged '83 Rabbit which scoots and does everything quite well. Overall, I have to say I've had more fun in my n/a RX-7 (with the carb) than I've had with the turbo bunny, in any venue-- drag, auto-x, track lapping or street driving. With this new improvement, it'll be even better. There's a lot to be said for being able to run 87 octane (that's what the haltech was tuned for, by the way) and the simplicity and reliability of a N/A engine. Don't feel that you won't have fun without a turbo. It's not at all true. =)

Wreckerx7

Richard Miller

j_tso

iTrader: (2)

That's awesome!

With no choke on the DCOE, the cold starts this winter alone made me want to switch to EFI.

Richard Miller

I thought the IDA had no choke. My references are the EFI style DCOE or square bore, not carbed.

Toruki

Love the video. Some folks have tried the FITech with 12A's and other "learning" type conversions but run into problems...never getting them quite right. This is obviously waaaay better and looks fairly "bolt on". The FI Tech one seems to have no provision for changing how the secondaries physically work (from what I can see in some photos on their site).

mikey D

73rx313b

iTrader: (40)

which Megasquirt did you go with mikey D?

Jager

iTrader: (10)

Very cool to see a definitive dyno.

What was the cost difference between purchasing the throttle body to replace the carburetor?

chuyler1

iTrader: (1)

The link to the video isn't working. Can you discuss any other modifications you've made to the car and motor to go from 116 to 162 hp?

73rx313b

iTrader: (40)

The car should have/ would have made alot more power with the Holley if they would have run it past 6k??? They nearly hit 8k with the second run.... That will explain why there is such a drastic gap between the 2... not saying you didnt gain any power but not that much brotha

chuyler1

iTrader: (1)

Yeah, 116hp from a streetported motor with pretty much any carburetor should have done better, hence my asking what else was done. I missed the RPM difference though. Wish I could see the video or at least some photos of the throttle setup.

Qingdao

iTrader: (3)

Right, no offence but that is a horrible tune on that holley. The climb is fine until 4k then it plateaus and shortly falls on its face. Was there any stumbling or sputtering at 7k when it was carbed?

At anyrate its good you have found what works for you.

mikey D

wreckerx7

Hi,
The only other change made that could possibly affect power was changing from belt-driven to electric rad fans.

Yeah, i noticed that, too. I can't play the video on my apple phone, but on the desktop computer it's fine. Not sure why.

wreckerx7

I can't confirm or deny that my Holley could have been tuned better. The first year I had it, the car ran horribly. I sent the carb back to RB, where they found some stuff wrong with it which was repaired and returned. A few more days were spent tuning. The difference was night and day. No more huffing fire out the tailpipe on downshift or letting off (kind of missed that, actually), no more full throttle stumbling... overall a big difference and enjoyable to drive. The first dyno plot was taken at this point, with an exhaust sniffer. 12-13:1 at WOT, with a brief bump to 14:1 as the secondaries open, then again between 12-13:1 up to redline. I've always imagined the first plot's joggle was the secondaries opening and the engine going from a 'power' a/f ratio to basically Stoich, then back to power.

Can a Holley put out a dyno plot like the second one? I don't know but I can say mine didn't after dumping a bunch of money into it. That doesn't mean that the wizardest Holley tuner in the world couldn't make it happen, it means that I won't be finding out the answer to that myself. I would point out that a carburetor has a lot more 'stuff' in the throttle bores than my EFI throttle body does, and that alone simply must mean that the Holley is more restrictive to airflow..
Did my car gain 'that much power' by switching from Holley to EFI. Sure. Look, the graphs prove it. Would revving the engine to 7800 in the first plot have brought the numbers up the the same level as the second plot? I doubt it. The torque was plummeting at 6200.

What would be interesting here would be for someone with a 12a street port, full RB street port exhaust and Holley carb/intake manifold that was 'fully tuned' to provide us with a comparative dyno chart. I am actually quite interested in knowing what the RB Holley can do, as mine clearly wasn't doing whatever that supposedly is. Without the proof, it's pretty much only speculation. I thought my car was pretty good before EFI. (except in very hard left corners on R compound tires, where it would stumble briefly) and now it's a **** ton better. =)

Qingdao, the car ran great except for real hard left corners. Listen closely to this, you can make it out twice, about 1/2 to 1 second of hesitation when powering on for corner exit: (7000-7500 rpm shifts, by the way)

Chuyler1, the only other change made between the two dyno sessions was replacing the belt driven rad fan with electric.

JSmall

That does seem a bit of a large gap aye. Who knows what may of caused it. That video above - I just kept picturing the Speed Academy boys flying past hahahah

t_g_farrell

iTrader: (1)

Typical RB Holley story that I have heard over and over through the years. Good to see you found something that works for you.

My stock port put down 134whp with the Dellorto and about 124 lbs torq at about 7000 rpm. Now I have the hogged out Nikki and its has a better feeling torque curve, torque from idle all the way to redline feels constant and it revs much quicker to redline as well. Also no bogs or hesitation on corners or acceleration. I would expect with a good sized SP on it I would see 150 to 160 whp, a good port and tune can pick you up 20+ hp.

An uncurable trait of a Holley on a rotary. Nuf said. Its too bad you had to experience all of this and waste the time and money as well.

chuyler1

iTrader: (1)

Please PLEASE post some photos and more info of how you made the secondaries vacuum actuated. The video link doesn't work, is it posted on Instagram? If so, what account so I can get straight to it.

wreckerx7

chuyler1

iTrader: (1)

Sent request the other day, still waiting to be accepted.

wreckerx7

Toruki

I use a desktop, the video worked initially but now there is an "Expired URL" error message. I can describe what I saw in the video if that helps...The secondaries were actuated by a completely separate pushrod, presumably removing whatever mechanical linkage had been there between the primaries and secondaries. The new secondary linkage was actuated by a dedicated vacuum diaphragm, electronically controlled via a solenoid via the Haltech.

chuyler1

iTrader: (1)

So is there any kind of safety return when you lift off the throttle? Or it's up to the ECU to shut it?

wreckerx7

Ok, let's use this link: should work for anyone not in China.

73rx313b

iTrader: (40)

Your Secondaries are not opening more than 1/4 at best from that vid anyway??? could it be that the two dyno sheets are backward? that would explain a drop off atv6200rpm??