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Awesome vid! Really cleared up the whole 'hot air issue' with an intake change.

I recently bought your kit without the speakers and found out the holes wernt premade, what's the best way to go about lining it up and cutting them

leroyengineering.com/pages/leroy-miata-cup-2025

I removed PS and A/C from my eclipse. Not a night and day difference, but you can feel it

I think it would be interesting to see how the power is affected with the steering wheel is turned back and forth (maybe air down the tires significantly on a run to see the correlation more clearly). The steering wheel being turned full angle one direction might not be realistic but you could validate this by turning the wheels back and forth

Absolutely gorgeous work. Would love to restore my 95M one day

Love when people do analysis like this! TY

what type of hard dog roll bar is it? and where can i buy it? i know i can buy it online, but i want the one you used on the video, so the rear speakers can fit on perfectly.

Can you tell me if I have a real gain if I put an Apexi AFR on my 1.8 nb2 I just have an intake cone on my car and running 40k miles today Thanks in advance 🙏

Very interesting video!

I saw this car probably 90% complete in person. ...as good as it looks here, this video does not do it justice. They guys at Leroy are top notch. I went to them with the worst situation to be in with a mechanic..."she dosent run, IDK why". If you dont understand its because diognostics and hunting for a problem is a prime way to end up in HUGE bill territory. Jonathan was upfront, fair and transparent with a detailed cost break down and options of his cost VS diy. If you have Miata problems, take it to Jonathan and Tim at Leroy!!

This a beautiful car. The owner is very lucky to get this quality of work done. We are very lucky to have someone in Ohio like Leroy Engineering. I am so curious what a build like this costs. Do I need to call to get a ballpark figure..

Looks great, I was surprised you left the powertrain bone stock

that's pretty checked out

leroyengineering.com/blogs/past-projects/1991-custom-restoration-mazda-spirited-green

Any chance you could test hp gain if any from an electric vacuum pump hooked up at the PCV valve cover to reduce crank case pressure on a naturally aspirated setup?

Would like to see a bellmouth velocity stack test with these intake lengths.

I wonder if the MAF was on the other end would the results change?

how much weight does it add?

Hey man! I guess the best mod for 1.6 miata, stage one, is going with electric water pump, electric ac compressor, as well as electric power steering For AC compressor I should say, it's bit heavier than your factory setup(~15kg, with back strapped AC radiator/fan). If you're ok with it, then based on the cockpit space, I recommend at least 2btu for a 2door small pickup. I have done only one of this sh¡t, but I researched it, like an asshole police, searching your car, without consent, just looking for sth to charge you with! I used a 4.5btu for my hatchback. I tasked it with ac, one giant ~1.4ft³ refrigerator, and one other thing. It uses 24v( with 3 separate small units of 12v DC to 24v DC convereors). For the power steering, so far, my best result had been combining both direct electric motor with mazda3 electric hydraulic pump, with my factory hydraulic rack). There is just one small pushback for above-mentioned upgrade: the efficiency of electric motors are less than their mechanical counterparts! Therefore while using them actually you are putting all the load on your alternator and with one step, on your engine! The way to attack that's problem is having a shot down/off push key under the accelerator, killing the alternator while heavy acceleration! So it won't affect your engine's performance!!! Please don't mention weaker sparks, because there are zillion ways around it. 😅 Doing so, on average you might gain 20hp optimistically, but this 20hp, is more than 20hp gain, achieved by upgrading turbo for example! Because it reduces the engine load, instead of putting much more strength on it! So no more powerful cams, pistons, conrods, etc.

hate manual steering and hot tyres

I just did mine last week when I was doing my timing belt and all 16 were stuck solid. Smart using that valve seal puller. I struggled to get mine apart taking over an hour. I also didn’t realize it was so easy to get the inner plunger apart. I soaked mine over night in seafoam.

Yeah that’s pretty interesting. I removed the power steering on my 90 last week. For now it’s just looped but in a few weeks I plan on finishing the job. Was waiting on new SuperPro bushing for the rack. For me I didn’t notice much of a performance difference. I don’t have A/C but I’m sure there is but it wasn’t noticeable. As it is looped I like the weight of it driving. It’s on the heavy side bellow 20km/h but driving it’s really nice. I think there’s probably still too fluid inside though. If I hit a bump well making a hard turns at low speeds it kicks back a little but it’s manageable. Roundabouts are two handed now lol. The most positive thing is now it’s super easy to access the heater pipe to change that o ring 👍

What I gather is that increasing your intake air temperature actually advanced the timing. If you were running 87 pump gas instead of high octane, the cooler intake temps (from the first graph) would have likely made more power. Cooler air is denser, usually leading to more power, but your results differ likely due to the stable burn of high octane fuel, which effectively slows down combustion (like retarding timing). Running lower octane gas might have advanced the timing. If you had adjusted timing for the cooler test (graph 1) until it just started pinging and then backed off a degree, the cooler intake test would have shown more power. Running even higher octane fuel, like C16, would produce less power unless timing was further advanced. Remember, the key advantage of higher octane fuel is allowing more timing advance. LOL I said that origionally so bad and then ran it through ChatGPT to explain what I was trying to say. This is what chatGPT reworded what I was trying to say.

5:55

Wat size speakers

What Color is the valve cover? And is it powder

Well, yeah, of course you got a test of an electric power steering pump helped gain this horsepower

Nice job.

Nice. Any undercarriage shots?

Hey guys... great simple tests. Love the wrap up you do! I race an NB1 RS with standard spec engine ECU etc down here in NZ (feel free to see my Videos :) )... I have a square top inlet plenum I picked up and have grafted a skunk type (bigger) throttle body (removing and smoothing aluminium to transition nicely). My question is, should I stick with the VICS (as your car uses) or are there extra BHP's in the Square top... also, how bad does driveability get down low, will I regret the squaretop pulling out of slower corners or are the gains at high rev's just too much to resit the change? i.e. can you please test a square top inlet against the VICS inlet. Thank you!... I'll dedicate my first win to you if it all come together. Keep up the great work!

And/or parts updates

Dude, more garage update videos please

Manual rack has way better feel on corners least with the older stuff I used to drive, but I can imagine with the heavier car and some sticky tires you can turn out to be a pain in the parking lot

Niceee!!! I was conscient that the power steering pump takes some hp away, but i wasn't expecting to take that much OMG, specially when in full lock. Love your videos, could you make a video testing the diferent octane fuels and if more octane influences the hp, or not. Thanks keep the good work

Will it work with the NA stock air box?

I did the short method I’ve bought the car like 3 weeks ago and I’ve changed the spark plugs with ngk blue ones at the same time as the air filter (simota) and I think I ve gained some power if there is any1 here to tell me that the ngk plugs added some power let me know … cause I dont

De - Powered vs manual rack is different.

❤ this. Amazing work! Another YJ saved from being lost forever 👏🤩⭐️

The short ram is gonna suck hotter air while the longer (if done right) take colder air from outside the car is gonna have air thats more dense then the hot air thats expanded inside the engine bay

Excellent, thanks for sharing ❤ what's the make/part no. of those valve seal pliers? I've seen others use locking needle nose pliers, but your tool looks far better and less likely to cause damage

springs still sound a little stiff for a car that weighs so little

another interesting video, you guys honestly have great content

Awesome content, im so glad i discovered this channel, this is the type of testing we need to see more of instead of companies making blanket statements about what their products deliver.

subscribed😎

Back in 95 I bought an R model (94) with AC. Steering was a little heavy if barely moving but autocrossing had great feel and wasn't tiring.

How long were the pipes? the Honda K24 reaches max power at 900-1000mm length

I would love to see a video comparing the randell intake design, a intake taking cold RAM air from the front, I wonder what a intake that uses RAM air to provide more air quantity effects the HP output?

Great video. Would be interesting to try some water meth injection to see what that would do to intake temps and power.

We need a exhaust cam in the intake slot test