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XR4TI GRM $2k Challenge build
#1

I thought I'd post this here as I go through this process of building an XR4TI to participate in the Grassroots Motorsports Magazine $2000 Challenge.  For those that don't know, the magazine hosts what equates to a cheap car challenge ($2k all-in with some exceptions) of buying and building cars to compete in autocross, drag racing, and a concours judging.  It attracts some very creative and highly competitive builds; sometimes the kinda stuff that absolutely baffles and amazes. I've been a fan since its beginnings, so I've always wanted to build an XR to compete.  Here it is.

I originally purchased this black XR, which I call the MadMaXrati, in 2017 as one of a pair of abandoned and damaged XRs from a local outdoor storage yard for $350. This car had an engine and non-functioning C3 trans, the other was just a rolling shell.  After buying them, they then basically sat until this year's challenge (2022) in October.  I gave myself way too little time to make it happen and it was essentially a failure, but the 2023 dates are just 6 months away, so I'll be working to build as competitive a car as possible.  At this point the car does finally run and will move under its own power. I should also mention that it has some good parts in it from the previous owner like Cosworth 4 piston front discs, Cosworth sway bars, Leda & Eibach lowering springs, Koni yellows (blown I think), LA3/big vam conversion, aluminum rad (leaky as hell), some upgraded bushings and mounts, and a few other interior pieces.

In terms of the build so far, I've done some tune-up and maintenance stuff, replaced the head gasket (preemptively), added a Cosworth intercooler, completed a C4 trans conversion, upgraded to longer wheel studs, hacked the fenders to fit the wheels/tire setup, and stripped the interior.  At this point it's all about development and improving performance. Current plans include... and I'll be asking for input from the TurboFord braintrust on this stuff:

Microsquirt conversion
upsize the injectors with a either an FMU or adjustable fpr
port the E6 manifold
maybe try my hand at porting the head
turbo upgrade (eBay t3/t4?)
BMW e36 lsd conversion, 3.91 ratio
3" exhaust
some exterior stuff (fender flares, lexan/plexi windows, foxbody Saleen spoiler, might make my own Cosworth upper)
some interior stuff (race seat, flocked dash, add some gauges, etc.)
make sure everything else is good and works correctly

Again, all of this has to be done under the $2k budget, and it's going to be tight as I'm already around the $1300 mark now.  The goal is to get the weight down as far as possible and make 300-350hp. As hopeful as I might be, the event is so hyper-competitive that I really just want to put on a good showing with the car as a what's possible with a turbo Ford and the XR4TI. In terms of actual performance, I'd like to pull a low 13 quarter (or better), be in the top half of autocross times, and make a good impression in the concours.

Now some pics for your entertainment:

How I found it (it had a shattered sunroof and had been open to the elements for years):

   


Where I got it to by the end of this year's Challenge event:

   

More to come as I start prep again...
'89 XR4RS
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#2

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Sounds like fun, Wyatt ~ BUT, I don't understand your workaround for "upsizing the injectors" by using an $$ FMU. If you click on MY link in the (other) "DIY Adjustable FPR" thread that you posted to........you'll see that cheap 52pph low-z Bosch injectors are J/Y-available, along with the basis for a homemade AFPR, from mid-80s CFI 5.0L Ford & Mercury vehicles. With the AFPR, you can fool the 52's into being larger by simply cranking up the base fuel pres, but you MAY need a bigger pump.

The problem with putting all that extra fuel into the engine, is that you PROBABLY won't be able to get enough matching airflow thru even a large VAM. That's where you'll need the proposed Microsquirt in order to ditch the VAM with speed-density engine management ~ which you can get in kit form and save some money. Also.......I suggest a hood-exit "UP" (up pipe), instead of a more-expensive "DP" (down pipe) and full exhaust). Aside from being cheaper, it would also be lighter and more efficient.

BTW ~ pics, such as your intended "before-and-after" shots, can't be directly posted on TF without being "hosted".........either in the TF photo album, OR by an offsite hosting platform, like Imgur, etc.. <shrug>
Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI
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#3

(11-21-2022, 12:01 AM)TurboRay Wrote:  .
Sounds like fun, Wyatt ~ BUT, I don't understand your workaround for "upsizing the injectors" by using an $$ FMU. If you click on MY link in the (other) "DIY Adjustable FPR" thread that you posted to........you'll see that cheap 52pph low-z Bosch injectors are J/Y-available, along with the basis for a homemade AFPR, from mid-80s CFI 5.0L Ford & Mercury vehicles. With the AFPR, you can fool the 52's into being larger by simply cranking up the base fuel pres, but you MAY need a bigger pump.

The problem with putting all that extra fuel into the engine, is that you PROBABLY won't be able to get enough matching airflow thru even a large VAM. That's where you'll need the proposed Microsquirt in order to ditch the VAM with speed-density engine management ~ which you can get in kit form and save some money.  Also.......I suggest a hood-exit "UP" (up pipe), instead of a more-expensive "DP" (down pipe) and full exhaust). Aside from being cheaper, it would also be lighter and more efficient.

BTW ~ pics, such as your intended "before-and-after" shots, can't be directly posted on TF without being "hosted".........either in the TF photo album, OR by an offsite hosting platform, like Imgur, etc..  <shrug>

First, thanks for the reply and input.  I initially inserted the pics using Google photo links, but wasn't sure if that'd work here. They do show for me, but I've corrected it by uploading them.

I did find your post on DIY afpr shortly after making this post, so that's my plan now. Also, I've harvested several pairs of CFI injectors over the years, so I will have to see which I have (46s or 52s, can't remember). The previous owner has already installed a Walbro 255 high pressure pump, so I'm hoping it will be adequate for the pressures needed for the levels of fueling I'll need. And getting rid of the VAM and gaining tune-ability is a priority. I was considering going with a Moates E3 chip because it easily fits in-budget, but I think the flexibility and options Microsquirt offers makes it worth the budget hit.

As for the downpipe, it will depend on the turbo(s) I end up using and the style of turbine housing. I'm not really fond of the hood-exit option for a number of reasons (including that I may eventually v8 swap the car), but I also like the option of being able to fit a full exhaust on it to drive it on the street.  Also wonder if hood-exit might not go over well at the concours portion. That's a thing too after all.
'89 XR4RS
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