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Search found 1630 matches

by peejay
Sat Dec 12, 2020 5:02 pm
Forum: Vintage/Classic/Historical Engine Tech
Topic: Well they finally did it
Replies: 41
Views: 1728

Re: Well they finally did it

With Biden as President, the US will be right behind you. Our EPA was already planning on making it illegal to modify any production car for racing purposes. Even if it would never see anything but a track. When Trump put his people in the EPA, that went away . Biden's EPA picks will be even more u...
by peejay
Sun Nov 29, 2020 1:52 pm
Forum: Engine Tech
Topic: Oil pump gears. Helical or Straight cut
Replies: 4
Views: 400

Re: Oil pump gears. Helical or Straight cut

Helical gears would put a thrust load somewhere in the system. Slots like that are good for lubricating the shaft they ride in. The engines I play with have gerotor type pumps and the shaft is located by a bore in cast iron. An old racer who'd been building these engines literally since I'd been bor...
by peejay
Sun Nov 29, 2020 1:44 pm
Forum: Engine Tech
Topic: How Radical Is Your Naturally Aspirated or Nitrous Street Car with Full Accessories Including A/C?
Replies: 45
Views: 4117

Re: How Radical Is Your Naturally Aspirated or Nitrous Street Car with Full Accessories Including A/C?

Not cheap, either. If I bought a Hellcat and threw some more money at it, I could run comparable ETs and have AC for the drive to & from the track. But then I'd have a big(ger) hole in my bank account, too. Not my daily driver, so it's much simpler to save the $ and keep sweating on hot summer trip...
by peejay
Sun Nov 29, 2020 9:13 am
Forum: Engine Tech
Topic: How Radical Is Your Naturally Aspirated or Nitrous Street Car with Full Accessories Including A/C?
Replies: 45
Views: 4117

Re: How Radical Is Your Naturally Aspirated or Nitrous Street Car with Full Accessories Including A/C?

Having something radical with all the fruit these days is practical and not hard. Not cheap, either. If I bought a Hellcat and threw some more money at it, I could run comparable ETs and have AC for the drive to & from the track. But then I'd have a big(ger) hole in my bank account, too. Not my dai...
by peejay
Sun Nov 29, 2020 9:08 am
Forum: Engine Tech
Topic: How Radical Is Your Naturally Aspirated or Nitrous Street Car with Full Accessories Including A/C?
Replies: 45
Views: 4117

Re: How Radical Is Your Naturally Aspirated or Nitrous Street Car with Full Accessories Including A/C?

For years I drove a car that built 4" of vacuum at a 1500rpm idle. I could get it to idle down to 1200 but vacuum dropped to 2" and throttle response was "soggy". No A/C because I bought the car out of Wisconsin and the previous owner removed the A/C. Next one I bought came from Alabama. I only boug...
by peejay
Wed Nov 04, 2020 6:47 pm
Forum: Engine Tech
Topic: Weak part throttle performance
Replies: 41
Views: 1319

Re: Weak part throttle performance

Not just timing curve, but also vacuum advance curve. Tee in about six-eight feet of vacuum line and stick a vacuum gauge on the windshield and see how much vacuum the can is actually getting at part throttle. Then duplicate that with a vacuum pump and see just how much timing you are getting. You m...
by peejay
Tue Nov 03, 2020 7:51 pm
Forum: Engine Tech
Topic: Question about EFI cold start AFR
Replies: 54
Views: 1499

Re: Question about EFI cold start AFR

As has been mentioned you need to compensate for the loss of fuel due to the cold intake and poor evaporation of the fuel at startup. Current ecu's will allow you to automatically compensate the fuel loss at cold start. It does so to reach the set AFR goal. That is basically still what you always r...
by peejay
Tue Nov 03, 2020 7:45 pm
Forum: Engine Tech
Topic: Question about EFI cold start AFR
Replies: 54
Views: 1499

Re: Question about EFI cold start AFR

I'm trying to picture how a cold engine, with the same airflow and ignition timing as a hot engine, runs 200 rpm faster cold vs hot just by richening things up. Simple... if the engine is more powerful with a rich mixture, it will idle higher. I used to use this as a cold start idle-up, by having t...
by peejay
Tue Nov 03, 2020 7:16 am
Forum: Engine Tech
Topic: Question about EFI cold start AFR
Replies: 54
Views: 1499

Re: Question about EFI cold start AFR

If it feels like it is lean stumbling, it's not getting enough fuel. Seat of pants tuning, no precision needed. No direct airflow measurement, just a "calculated guess" speed density system. I am thinking the enrichment is simply due to the engine having higher VE when cold because the entire intake...
by peejay
Tue Nov 03, 2020 6:23 am
Forum: Engine Tech
Topic: Question about EFI cold start AFR
Replies: 54
Views: 1499

Re: Question about EFI cold start AFR

Correct is "what it needs". This is going to depend a lot on your fuel injector spray pattern, injection timing, port geometry, injectior location and geometry... My engine actually likes the same air/fuel ratio dead cold as hot, according to the sensor. However I still need 20-30% enrichment to get...
by peejay
Sun Nov 01, 2020 11:23 am
Forum: Engine Tech
Topic: Lowering octane
Replies: 19
Views: 943

Re: Lowering octane

Dyno a motor on 91 then 87. Made more power on 87(8.5 cr).How can you lower the octane even more? Kerosene? Mazda used to mix race fuel and kerosene to make an 80 octane blend when they were racing rotaries in IMSA GTU. Closer to what us mortals can do, I've always been a fan of A-B-A testing diffe...
by peejay
Wed Oct 21, 2020 10:17 pm
Forum: Engine Tech
Topic: Ignition advance at cruise rpm?
Replies: 44
Views: 1797

Re: Ignition advance at cruise rpm?

You may find that you can't get enough timing. You'd lose reliable ignition before you hit best timing.

A lot of engines had higher compression than ideal for WOT performance, so they could be more efficient under light load.
by peejay
Thu Oct 15, 2020 7:32 pm
Forum: Engine Tech
Topic: camel hump vs vortec
Replies: 27
Views: 1732

Re: camel hump vs vortec

I guess the question is if you are racing flow benches or racing cars. I think one of the worst things is the idea some people keep repeating, that "engines are air pumps". They really aren't, that idea ignores combustion, acceleration, and is only one dimensional, ignoring the dimensions of RPM and...
by peejay
Tue Oct 13, 2020 7:01 pm
Forum: Engine Tech
Topic: camel hump vs vortec
Replies: 27
Views: 1732

Re: camel hump vs vortec

Flow is flow but velocity matters too, and the Vortec chambers are waaay better, they burn faster so you need less ignition timing.