How to build an effective splitter for only $100

Our LS-swapped 350Z has sat quietly while we’ve worked on its digital twin, one built in CAD. Without getting our hands dirty, we’ve virtually tested all manner of aero add-ons: wings and splitters, vents and dive planes. 

One big takeaway from our time in Morlind Engineering’s virtual wind tunnel? We needed to build a splitter. 

And while we arrived at …

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So, what's the source for this proprietary "rocket nose coating"?

In reply to Shawn_D :

NLR said it's a trade secret, but it's a pretty cool process. 

"And if the front of the splitter deflects enough to touch the ground, it will block all airflow under the splitter. No airflow means no downforce, which is why a flapping splitter can suddenly remove all front downforce mid-corner. That’s bad."

I'm having a difficult time visualizing why this is true.

Also, is a flat bottom side to the splitter the best shape? Wouldn't a curved wing like airflowish like shape be preferred?

This may be common knowledge but my buddy ran a nascar truck team for a minute and they set up their suspension so the splitters just touch the ground.   Of course they're not deflecting but the truck compresses in the corners, lowering it so it scrapes.  And they're thick - they are not folding down.  
 

To VolvoHeretic: it is not a case of the splitter touching the ground removes ALL downforce, just that it reduces the downforce by a very large portion (~30% is typical). The downforce is generated by the air reacting on the bottom surface at increased local speed. On the flat vs curved surface question, there is a case to be made for non-flat surfaces, but the first 90% of performance can be had with a simple flat shape. After that testing and development are required to get the rest.

To jfryjfry: On the trucks, the splitter is just under 1/2" thick so it does have some stiffness benefit over thin materials. However, the material spec'ed for the Truck series is not the stiffest stuff out there. It does deflect. Setting the trucks up to just touch the splitter to the ground is typical, but generally only happens on the first few laps with low tire pressures. The peak downforce occurs with the splitter not touching the ground (by a small amount, less than 1").

I post this while I am waiting for the wind tunnel to give me the green light to start my test this morning...

In reply to VolvoHeretic :

we need air to make aerodynamic parts work. we can reduce the amount of airflow to manipulate the speed of said air. But if we seal off the airflow (by touching the ground), we are working in a vacuum and have no air to make the parts work. 

In reply to jfryjfry :
also, NASCAR is another level. they generally want as little drag as possible. Because 200mph. also their splitters are quite short (depending if we are talking about cup or Xfinity). They will do things slightly differently than club racers should. One thing is for sure,  no matter the class the height of the splitter is very important to downforce. The lower the better, but once it touches the ground you lose all downforce. get it low but not too low.    

Great article, thank you. Does anyone know a source fro the venturi's that were added to the splitter but not mentioned?

Or an alternative, as those CF Morlind ones look expensive! :)

I checked Morlind site and you can't buy from them, well Joe Public can't, it seems.

 

Yep, you can get the plastic versions right here:

https://9livesracing.com/products/nine-lives-plastic-splitter-ramps-by-morlind-engineering

GRM+ also removes the vast majority of the advertising on the site, and gives you access to our archive of digital editions going back something like 20 years.

We don't sell your data--we sell subscriptions. 

If you don't want to subscribe, that's fine, and there's plenty of free articles to read and a free forum to be a part of. But "paying for words" is sort of how a publishing company works.

Tom Suddard said:

If you don't want to subscribe, that's fine, and there's plenty of free articles to read and a free forum to be a part of. But "paying for words" is sort of how a publishing company works.

I'll add that the words you pay for are only the last step in a process that involves manpower to build those project cars that are being written about, and time/resource when testing is involved.  What are those hours and data worth?  Could you generate that same data yourself for less?  That's the value proposition.

Driving4fun said:

Another old article (2022) reposted in 2024??? 

Was this article actually re-promoted or are you unhappy that forum member "Rgvkiwi" commented on an 2 year old thread, bumping it up to current times? 

TJL (Forum Supporter) said:

Driving4fun said:

Another old article (2022) reposted in 2024??? 

Was this article actually re-promoted or are you unhappy that forum member "Rgvkiwi" commented on an 2 year old thread, bumping it up to current times? 

 

The former.  Part of a regular program to redistribute "oldies-but-goodies".

I'm speaking in a generally board sense here when I approach this topic.  YMMV. 

With the prevalence of "free" content these days, it seems very antiquated to suggest that subscriptions are what keeps an establishment afloat.  I understand the GRM community is a large part of the draw to this site but "donating" X amount every year to support an establishment that creates content which could be considered common by today's standards, is poorly spent imo.  Every subject and topic regarding anything automotive related has been covered ad nauseam at various corners of the internet for years.  It's how the saying "there's nothing new under the sun" is generally true in a historical context and I don't think members/enthusiasts should have pay to read about the newest tire review.  Not to mention that there will be no shortage of anecdotal/empirical reviews from countless sources all over the internet when said new tire debuts, etc from every day car enthusiasts to pro drivers acting as brand ambassadors. 

This is obviously subjective, but as I stated earlier there are well established forums that offer a 'pay to play' feature which then grants special access to specific site privileges.  The same type of forum where members share all kinds of experiments/experiences that you do not have to pay to get special access to read them.  They just felt like sharing as many people like to do these days.  

ps- I appreciate this site and the work that goes into keeping it running.  I'll refrain from commenting about any disappointments in the future.  

I'm not sure I understand the nuts and bolts of your argument- are you purporting that the dudes who run this magazine should create and distribute content for free? Because there are others out there who just do it for free product? 
 

You've got Andy Hollis, James Clay, Tom, JG, etc. these are *professionals*. The other guys are shilling product. These guys are the real deal. 

Driving4fun said:

I don't think members/enthusiasts should have pay to read about the newest tire review.  Not to mention that there will be no shortage of anecdotal/empirical reviews from countless sources all over the internet when said new tire debuts, etc from every day car enthusiasts to pro drivers acting as brand ambassadors. 

To my knowledge, there are only three sources of comprehensive, unbiased, scientific third party comparison tire data on the web: GRM, Tire Rack and Jonathan Benson's Tyre Reviews. 

Of those, GRM is the most comprehensive because TR only publishes tests for tires they sell and TyreReviews is Euro-centric (though Benson is now based in the US, so that will likely change).

TR provides that service "free" with the hope that you will purchase from them. 

TyreReviews is Youtube based, so it's only as free as the ads you have to watch during an episode or the YT Premium fee you pay.

GRM is free after a paywall period...you only pay (or subscribe) for early access.

If you just want to hear anecdotal data from random competitors or biased brand ambassadors, you are going to be several steps behind the early adopters.  But the pointy end isn't for everyone, so that may be the right fit for you.

Teh E36 M3 said:

I'm not sure I understand the nuts and bolts of your argument- are you purporting that the dudes who run this magazine should create and distribute content for free? Because there are others out there who just do it for free product? 
 

You've got Andy Hollis, James Clay, Tom, JG, etc. these are *professionals*. The other guys are shilling product. These guys are the real deal. 

Did you forget Randy fukin Pobst?

On topic, what do the ramps *do* on a splitter? 

The knowledge of this article is just as relevant today for those of us who haven't read it before. It's the same reason I keep and read old car magazines instead of throwing them out each month. I mean, after a couple of years, not to mention 30 or 40, old magazines are just as worthwhile in the bathroom as every.

DjGreggieP said:

On topic, what do the ramps *do* on a splitter? 

And are the ramps the part that are just behind the bumper structure that kind of directs the air to the suspension?  

Also, can you remind us if you put dive planes on the fenders?  I just can't recall off the top of my head.

In reply to DjGreggieP  and AlfaDriver:

The ramps on a typical splitter work to focus the low pressures generated near the leading edge and attempt to pull flow up away from the tire contact patch. There is a high pressure area just in front of the tire that is effectively drag. Using the low pressure under the splitter to offset some of that high pressure results in less overall drag at the same time that it is contributing to downforce.

On some splitters with ramps further inboard the effect is to turn the flow upward to assist with cooling of things like brakes and exhaust.

Overall the ramps are attempting to extract maximum pressure reduction, before stall, to generate the most downforce for a given shape and ground clearance. You can use more aggressive ramps for splitters that are further from the ground. For low splitter gaps the expansion is limited by the mass flow under the car.

In reply to stafford1500 :

So the ramps are the turn up just in front of the wheel based on the description of what they are supposed to do, right?

In reply to alfadriver :

Yes. They, like all aero bits, have multiple names. Splitter diffusers, splitter ramps, etc.