Running without the restrictor
Surely someone has done this by now.
Our club is running split weekends, so on Saturday, September 26th, I'll run my last 3 FF races of 2020...
...and then I'm going to run as a Formula Libra ("Libre"?) on the 27th.
So I'd like to run without the restrictor.
Has anyone tried this? Does the ECU allow it? Other than being geared to short, are there any other downsides?
Downside... it's addictive.
ECU can handle it. (how would i know)
Honestly, I think I can handle it (said every addict ever).Originally Posted by Purple Frog
That's all I needed to know!ECU can handle it. (how would i know
Still no spectators allowed ? My car is still in 1000 pieces but it would be nice to at least get a taste of the track this year.
Blasted bug !
Greg
I'm allowed one crew member, Greg...
Definitive answer to running the Honda without restrictor
From QuickSilver:
AlanSo there you have it.
Yes you can run the engine without the restrictor. Just make sure to use 93 octane fuel set the fuel pressure to 50 psi an it will make about 135 hp.
Have fun
Erik Oseth
What is the normal pressure for a Honda engine?
I don't know. I'm going to install a gauge on the fuel system and check what I'm getting, but I'd bet it's more than that.
You will want to adjust the gear ratios, otherwise you likely will spend quite a bit of time on the rev limiter.....
Yup!
I say it depends on the track. Since the redline will be the same, you'll just go through each gear quicker. Seems to me each shift will be at the same place on the track, only you will get to that spot quicker. The issue will be on top gear straights, On that straight if you just touch redline before braking, no problem. Big tracks where you might be dwelling a few seconds on the rev limiter, then change gears.
As always YMMV I could be FOS
I knew a guy who did it once and he definitely needed more gear.
You will be shifting earlier on the straights not only in time, but in position. So gears will need to be modified so you are not making extra shifts just before the next corner
Also in addition to a taller 4th gear on the straights, you will probably need to raise them all (except maybe 1st) so the splits are not screwed up.
Dave Weitzenhof
If it were for more than a little of end of season fun, I'd start worrying about the splits, but as it is, I think that the way I'm currently geared, I can probably get away with leaving 1, 2, and 3 unchanged (all three shorter straights don't get too near to redline in 3rd), and I'll just swap out 4th for a taller ratio so that I'm not bouncing off the limiter for a while at the end of the main straight.
I've got no clue how much of a change to make, but I'll figure on perhaps 5-10mph faster towards the end of the straight and so the ratio should change in proportion to that:
New ratio = Old ratio * 110 / 115-120
I've got a 19:24 (1.263) in there now, so maybe from a 23:28 (1.217) to perhaps 21:24(1.143).
Frankly, I'd rather guess too tall than too short.
...Frankly, I'd rather guess too tall than too short.
Dave Weitzenhof
To much fun
I know a couple Gents here on the west coast that have tried it along with some Hoosier R60's. Way to much fun.
They usually should be running about 50 psi anyway, although I've seen fluctuations + or - 2 psi on average.I don't know. I'm going to install a gauge on the fuel system and check what I'm getting, but I'd bet it's more than that.
Running without the restrictor makes the biggest difference at the top of the RPM range, particularly on long straights. It doesn't seem to make a significant difference on bottom-end torque coming out slow turns. At Road Atlanta I think it's about 6mph faster down the back straight (I'm too lazy dig up the data). If you're running by yourself it's the equivalent of being at the tail-end of a multi-car draft. The time difference was about 1 second.
You can probably get away with the same 1st & 2nd but you'll definitely need a taller 3rd & 4th. Keep a closer eye on brake pad wear as you'll be harder on the brakes with the extra straight line speed.
And I'm already at a track that is notoriously hard on brakes...
Thanks for the thoughts.
With a 10/31 differential, I'm currently running:
1 2 3 4 17 17 21 19 33 28 30 24
(I'll be fascinated to see how that formats)
At 6750, 4th gear gives 115mph, and I normally finish the main straight at about 110, leaving about 5mph of headroom for drafting.
A 21/25 4th would move redline speed up 7mph to 122, and even without changing 3rd, my RPM would only drop to 5550 when changing up. I suppose I could move the 3rd up to an 18/25, but since I don't reach too near redline on any of the shorter straights that end in 3rd gear, I'm inclined to keep 3rd where it is.
Thoughts?
CarTest 2000
Here is a nifty little acceleration simulator with files for a lot of road cars, and the ability to create your own custom cars. It also has a gearing optimizer.
https://www.cartestsoftware.com/
It's not free, but it is very affordable.
Any corners on this track where you are holding a 1-2 or 2-3 shift for just a second to prevent shifting at an inopportune time? If so, I'd reconsider changing your 1st and/or 2nd. Corners where you are WFO wishing you had more grunt will change. Those corners where you are on limit of grip/talent it won't matter how much HP you have, you won't be going any faster so gear won't matter.
It's possible that between turns 1 and 2 that a little more power might leave me needing to upshift before braking again, but it would only be for a very short time; the whole "straight is only 3 seconds long.
2-3, 3-4, 6-7: I'll get close to the top of 3rd, but not close enough I think.
Anyhow... ...I'll give it some more thought.
Guys,
I did the math. If you use the same gears, the same shift point (rpm), and the same tires on the same track, the shift points will be at the same points on that track. The only way they wouldn't if if the added hp increased tire spin. What will happen is that you will get to each of those the shift points a tad faster. If you are currently happy with shifting at those points on the track, then there is no need to change the gears.
And the HP will allow you to possibly pull a taller 4th gear, if you were already at redline before braking at the end of the straight with the weaker engine configuration.
Not sure how that math worked out for you.
If I am using the same gears, same tires and same rpm shift point then I'm shifting at the same exact MPH, agreed?
Now, with my additional HP/acceleration I am attaining that same MPH in less distance and time, therefore will shift sooner than "normal" in both time and distance.
Time yes. Distance no.
Peter Olivola
(polivola@gmail.com)
Time and Distance.
Sent from my iPhone using Tapatalk
OK, let me see if i can explain Peter's (and mine) thoughts in less than a thousand words.
You are rolling along and hit 6900 rpm in 2nd gear. You shift to third. It takes the same number of crank turns from lets say a drop to 5800 rpm back up to 6900 rpm again. I'm saying the crank turns 'n' turns to accelerate from 5800 to 6900. It turns the gears and tires the same number of turns whether its 110 hp or 135 hp. So it travels the same distance from one shift to the next, regardless of HP. With more hp it gets to the same spot quicker, but it is the same spot.
**********
What i think Brandon and DaveW are saying: (correct me if I'm wrong)
Because of the extra 25 hp the climb from 5800 to 6900 takes less than 'n' revolutions of the crank. So one travels a shorter distance to reach the next shift point.
I see their point.
Remember this formula: Vf2 = Vi2+ 2ad ?
Now double "a". Final speed in gear is the same, so if you exit the corner at the same speed:
Vi2+ 2ad = Vi2+ 2(2a)d'
Solve for d'.
2ad = 4ad'
d' = 2ad/41 = d/2
Change the acceleration and the distance you need to achieve the same speed changes in inverse proportion.
In short, if you're getting to corner entry just as you get to redline...
...you'll need a taller gear if you don't want to shift.
(Or if you want to solve by embiggening: imagine an engine so powerful you can suddenly go from 5800 to 6900 rpm in a single turn of the crank!
There's a reason more HP gets you a lower ET and higher terminal MPH in a drag race (all else being equal).
Not only are you getting to the same spot more quickly, you're going faster when you get there (If you weren't going faster at any point along the track you wouldn't get there sooner).
Cheating is so complicated. Much easier to run as a legal FF as intended.
Greg Rice, RICERACEPREP.com
F1600 Arrive-N-Drive for FRP and SCCA, FC SCCA also. Including Runoffs
2020 & 2022 F1600 Champion, 2020 SCCA FF Champion, 2021 SCCA FC Champion,
2016 F2000 Champion, Follow RiceRacePrep on Instagram.
It's not cheating if you enter as FL as the OP stated he intends to do.
This is the FF section of the forum. I find it distasteful to post a blueprint for people that may want to cheat.It's not cheating if you enter as FL as the OP stated he intends to do.
I love the class the way it is. No interest in illegal mods.
Lots of other OW classes for those that don't like FF.
Greg Rice, RICERACEPREP.com
F1600 Arrive-N-Drive for FRP and SCCA, FC SCCA also. Including Runoffs
2020 & 2022 F1600 Champion, 2020 SCCA FF Champion, 2021 SCCA FC Champion,
2016 F2000 Champion, Follow RiceRacePrep on Instagram.
Fair enough.
Oh, crikey.
It's not exactly a deep dark secret that pulling the restrictor would result in more power...
...nor is it difficult to check if someone has done it.
I posted here, because here is where people who've tried it could be found, Greg.
I have followed this with interest. I don't plan on cheating but more knowledge never hurt anybody. Of course whenever someone beats me I wonder if he is cheating.
When I first came out to race at Mission it was rumoured that there was one driver whose engine might not have been legal. But once I was able to go fast enough to occasionally get out of a corner as fast as he did, it confirmed for me that it was nonsense. My RF89 was nothing special in the engine department, either.
Similarly, there was much scowling when I bought the Van Diemen Honda, but once we'd been out there and the other drivers discovered that my engine wasn't some unbeatable monster.
And not only does more knowledge not hurt... ...you can't prevent anyone who wants to find out something from finding it out!
Fuel pressure
No need to install a separate fuel pressure gauge. The Honda ECU supplies that data. It is listed as FF_FUEL_PR [psi] in the measures column. You can also access that data synchronously by connecting your laptop with the download cable while the engine is running and going to "Online" (AIM system) and find the value while the engine is running. If your pressure regulator is adjustable, you can adjust the pressure while looking at the value on the laptop.I don't know. I'm going to install a gauge on the fuel system and check what I'm getting, but I'd bet it's more than that.
Ah... ...but nobody installed the "Engine Sub Harness" on my car...
It's OK. I bought a little gauge I can temporarily install in place of the fuel sampling port.
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