Mods for 90's Citroen Break (STW for folks in US))

[jtbo]

My vehicle is perhaps bit unknown to US market as Citroen did pull out from US market before this car was introduced if my information is correct.

Here it is considered being small family car in US it would be probably something smaller than compact class?

Specs as follows:
Citroen ZX Dturbo Break 1997, motor code XUD9TE
1.9 litre turbo diesel motor, producing 90 HP and ~250Nm of torque that is 184.37lb/ft at 2250rpm.

length 4m (13.12 feet) width 1.7m (5.8 feet) height 1.4m (4.6 feet) 0.13m (0.43 feet) of ground clearance and we have legal limit of 0.075 (0.246 feet), tire flat and suspension compressed fully.

Car without modifications is now getting around 53MPG(US)

My driving is on highway, however our roads are not as nice as in some other countries, so we have lots of hills and curves, roads are narrow and often speed is limited to 50MPH, also my car has 50MPH limit on it's back.

I usually don't drive less than 100 miles when I start the car, so warming up does not affect so much to me.

Steep long hills do cause need of bit more cooling than flat areas, but it is rare that we get temps over +25C.


Took roof railings off and filled hood gaps, also gaps around front lights and taped lower portition of upper grille, upper portition brings cool air to intercooler that sits at top of motor.
Next weekend I should know if those had any effect, however conditions have been very windy so even to get same MPG as before is going to be less fuel consumption.

Photo is from Allcars.com

Here is how car looks as standard:


I did poor job of photoshopping what I would like to do:


From front:
Airdam, to limit airflow underside of car and to block part of lower grille, Plan is to run it straight down from foremost edge of bumper and to follow bumper curvature to sides, also lower edge of airdam should be bit lower than current front bumper is.
Issues with here can be that I'm increasing frontal area too much to have any benefits? Underside of car is rather ugly.

Front wheel well cover, just small one to make gap bit smaller, don't know if it would have any meaningless value, but I will be testing it with duct tape and cardboard.

Hood spoiler thing at back of hood, from red circled areas I hear lot of wind noise, I hope to guide air over those places, but I'm unsure if drawn location is good (it is bit similar in aerocivic), or maybe at front edge of hood it would be better?

Rear wheel well cover, top of wheel well is already made straight by factory, but I have seen many putting good covers there and probably for reason, should be rather easy to do and test.

Lastly, but not leastly, is extension of roofline, bolted to trunk lid, shape is what I thought would give some separation help and should perhaps function, but I'm the newbie here, don't know about much, I have read about 15 degrees, but I think it should also be bit curved as in original Kammback vehicle of 30's?

What is not seen is bottom of car, from front axle to front and from front of rearaxle to rear bumper area is a real mess, those I hope to cover with some material, I don't think that we have coroplast over here, so have to be creative about it. From rear I think little less angle and bringing bottom out a bit, so it is past bumper line, might work out well enough?

I have mudflaps and I'm hoping to make some miniboattails for front wheels so that I would not get so much penalty from mudflaps, car gets really easily very muddy from it's sides so I hope to get improvements to this area too.

Car has cd of 0.36 as standard, don't know how much roof railings add, but at least there is bit less noise, however wind still grabs car very hard.

This vehicle has no value as of money, it is very beaten up by unknown persons at the parking lot and during winter huge chunk of ice that flew towards me from big rig, took part of front bumper with it, so it is very ugly and nobody wants it, so it is pretty much same what I do with it now, however it is my main transportation and I need to haul lot stuff in it so trunk need to be usable as it is now. Good point is that there is full year of MOT (we have yearly inspection of vehicles here), probably will not pass next MOT without major work so this is rather free experiment.

Primary goal is to get off from boost at 50MPH, it is now 0.05-0.1bar on boost at that speed and getting any of boost will increase fuel consumption radically as that is nature of old tech diesels. Second goal is to get under 4l/100km consumption, that is to get into 59MPG(US), I don't know if these modifications will get it any better than that as shape, motor and gearing is what they are. Bigger tires did not go so well, added consumption by over 20%, car had not power to go up hills.

I'm interested in hearing your opinions as it is perfectly possible that I'm thinking something completely wrong here, I'm just 'going with the flow' meaning air flow and what others have done.

Beauty is in functioning form, ugly are chrome fashion and bling.

[JMPVW73]

Your thinking is correct but your wording is a bit odd.
You mentioned your country’s roads but didn’t say where you live. Your garage says Monaco; is that where you live?

Coroplast is not an exotic material. It is just corrugated plastic board and it will survive rain much better than using cardboard. A good source in the US is political election signs that you can pick up for free after voting is over. I don’t know if they have that sort of thing where you live but it shouldn’t be difficult to find for purchase.

[jtbo]

Originally Posted by JMPVW73

Your thinking is correct but your wording is a bit odd.
You mentioned your country’s roads but didn’t say where you live. Your garage says Monaco; is that where you live?

Coroplast is not an exotic material. It is just corrugated plastic board and it will survive rain much better than using cardboard. A good source in the US is political election signs that you can pick up for free after voting is over. I don’t know if they have that sort of thing where you live but it shouldn’t be difficult to find for purchase.

Monaco is actually trim level of my car, but I indeed live in Europe and in here it seems to be not so common material. It seems that our politics are still stuck into cardboard and paper.

I do have a welding machine and sheetmetal, so maybe using that, but it is lot of added weight then, I must research a bit if I can find something similar for coroplast.

First tests I'm thinking of doing with cardboard and duct tape, that way I get samples which I can cut more rigid material.

If it rains, cardboard will 'melt' so that is not good for anything else than quick testing. I really wish to find local source for coroplast or alike as it would be really easy material to work on.

[Piwoslaw]

Originally Posted by jtbo

Monaco is actually trim level of my car, but I indeed live in Europe and in here it seems to be not so common material. It seems that our politics are still stuck into cardboard and paper.

Unfortunately our politicians last for much longer than the cardboard they print their mugs on

Try looking for coroplast at shops that make advertisements, Groar found a batch of circus signs on the roadside. I found a plastics company which offered it - it's not called "coroplast", so I had to look through the pictures in the catalog. It's usually made from PP, PE or PVC, in different colors, sometimes you can find something that's UV resistant.

Originally Posted by jtbo

I do have a welding machine and sheetmetal, so maybe using that, but it is lot of added weight then, I must research a bit if I can find something similar for coroplast.

Before you start any welding, not only get the shapes and sizes right, but also find out what your local laws are. The US is much more relaxed about what you do to your car, while in Europe you must have all sorts of homologations and certificates for pretty much everything. It's supposedly safer that way, but for many it's just a royal PITA.

[jtbo]

Only their promises disappear faster than their carboard ads

Kammback design is perhaps one that might be bit shady ground according to law, rest I think should be ok.

This one was before Kamm, so maybe it really should be Ledwinka back?
Tatra 77 - Wikipedia, the free encyclopedia

Our police has been replaced by speed cameras, so much that even I spend 3 times more on road than average person, can't even remember when I did saw police last time and if there is a police they seem to be not very interested from mods, so even I get bit illegal side, there is much of real danger of getting caught.

However, I understand well other side, if someone drives over me and I have illegal mods, then I'm not getting much if anything from insurance.

I know that I can block rear window, but then I must have passenger side mirror too, which I do have.

It is also possible to have 'cargo' that is safely secured and not extending more than 1 meter over outline of car, if extending more, red warning flag is required.

Trunk lid/door is made from plastic, it is not metal at all if I'm not mistaken, so I'm thinking of screwing right trough it to mount that kammback thing.

I will try to find corrugated plastic for belly pan and front airdam might be good to be made from that too.

edit: I did found something that looks similar to Coroplast, it is made from pp, 6.56 feet x 9.84 feet is 62.05 toymoney (euros) + delivery which is not cheap either, probably over 20 and still I need to pick it up from 15 miles and I don't have anything to transport such big sheet, that was 8mm thick, there is smaller sheets that are 5mm thick, but those too are too long to fit into my transportation methods, maybe I could get them precut from them, that would save bit of hazzle.

[Piwoslaw]

I plan to contact whatever institution is responsible to find out how to make permanent versions of my mods legal. Just in case. So far the police has only been interested in taking pictures of my car, though I was close to failing my inspection once. If a police, border patrol or customs officer decides that you might be trying to hide something with your bellypan, or that your wheelskirts may fly off in traffic, then having papers for it will put you in a much better position during the discussion.

When I bought my coroplast I believe it was 2x3m (it cost around 30€, iirc??), so when I went to pick it up I had to cut it up in the parking lot. My advice is to know beforehand exactly how you'll want to cut it so that later you don't end up with bits and pieces you can't use.

If you make the kammback so that it doesn't extend beyond the rear bumper then you won't have to worry about red flags and such. I would love to have my rear window at the rear of the kammback to slightly increase trunk space. I've needed that space on more than one occasion...

Originally Posted by jtbo

Our police has been replaced by speed cameras, so much that even I spend 3 times more on road than average person, can't even remember when I did saw police last time and if there is a police they seem to be not very interested from mods, so even I get bit illegal side, there is much of real danger of getting caught.

Just because you don't see them, doesn't mean that they don't see you...

[jtbo]

Originally Posted by Piwoslaw

I plan to contact whatever institution is responsible to find out how to make permanent versions of my mods legal. Just in case. So far the police has only been interested in taking pictures of my car, though I was close to failing my inspection once. If a police, border patrol or customs officer decides that you might be trying to hide something with your bellypan, or that your wheelskirts may fly off in traffic, then having papers for it will put you in a much better position during the discussion.

When I bought my coroplast I believe it was 2x3m (it cost around 30€, iirc??), so when I went to pick it up I had to cut it up in the parking lot. My advice is to know beforehand exactly how you'll want to cut it so that later you don't end up with bits and pieces you can't use.


Just because you don't see them, doesn't mean that they don't see you...

That is probably best plan to cut it when picking it up, have to make plans for it before ordering then.

I spend so much time on road that I can spot their unmarked cars quite well too, but it is better to have mods perfectly legal.

I don't think that here they actually will even mark those mods even if asked, pedestrian safety is something they are bit frantic about, but with these older vehicles it is much easier, when it is well secured and has no sharp edges where person could hurt themselves, then it is ok by inspection.

But if one adds even bit of horsepower to engine, that is where things get problematic.

It would be nice to have officials to understand that it is best for all to make these improvements to vehicles, they should be helping instead of limiting, imo.

Reduction of police on road is supported also by statistics, resources are really low and they have priorized things quite a bit.

I'm going to put bellypan only under engine/gearbox and to rear part of car as between there is rather flat area, but I will need to put some sideskirts as there is so large area between tires that is curved too much inside.

Coroplast like material if only 5mm thick and 1.5m x 2.7m in size would be here price similar to what you got, but our prices here seem to be 3 times what they are 1000km from here, so maybe I have to think that I have found it cheap

[jtbo]

I did some prototyping, after reading that airdam should be as low as lowest part underside car and not more, I decided to put sheetmetal airdam, I readlly needed only about inch more over car's stock version and bit wider to guide air past tires, there should of been more curvature at ends, but had no time to make everything perfect, it is some scraps from roof building, screwed into bottom of bumper, it follows arc of bumper and enough for prototyping I guess.

Could use a splitter though.

Then I modified mudflaps and made them smaller.

I did put 'spoiler' on hood, rear part of hood I duct taped some cardboard, bit less of angle than what windshield is, it is about 6 inches long (font-rear wise) rear is lifted about 2 inches. Maybe tiny bit less wind noise, but no really big effect, imo. Maybe it should be more towards rear so that it is almost touching wiper arm, but I was afraid it would interfere with wiper then. Must examine this bit more before building final version, there is no more than inch of gap.

Then I did turn passenger mirror against window, cardboard and ductape made nice shield for hinge mechanism so it would not be so horrible aerodynamically.

Antenna was removed, that was forehead of roof.

Hubcaps installed to front.

Rear wheel wells were covered with duct tape and cardboard, also made bad attempt of partial kammback from cardboard and duct tape, cardboard was not best quality and it was curved, could not straighten it so sides were higher than middle, even I did added some supports that did not helped to get it straight from middle, so it might be better too.

Had not chance to make extensive testing, I did test that they should stay on place safely, there was quite bit of wind with very strong gusts so any proper testing would been pointless.

Can't really feel huge change, but then again at 50MPH there probably will not be huge change, however I did constantly overshoot my estimates when coasting, making need to use brakes where speedlimits did change, also wind seemed not to grab car quite so strongly as before, but I consider these feeling rather pointless, it can be that all changes just added as much weight than what possible gain there might been if any and as weight improves coasting too, it might been that also.

Forecast shows no rain for long time, so I'm hopeful that I can keep prototypes on for my next business trip, then if weather really stays similar, I could get nearly 600 miles of test driven on same roads that I did last tank of fuel, maybe improvement shows there or then not.

However for that trip I will need my passenger side mirror as it is really difficult to drive without one, it is like driving one eye closed

[euromodder]

Originally Posted by jtbo

Can't really feel huge change, but then again at 50MPH there probably will not be huge change, however I did constantly overshoot my estimates when coasting, making need to use brakes where speedlimits did change

This means the mods are working, but you haven't adjusted yourself to them yet, and so you don't gain as much as possible from them.

[jtbo]

Originally Posted by euromodder

This means the mods are working, but you haven't adjusted yourself to them yet, and so you don't gain as much as possible from them.

I hope that it is so, it took whole roll of duct tape and lot of waste cardboard, lucky me I don't throw anything away

Sadly one butterfly lost his life, first start to fly around here and this one hit my windshield, I could not see any change of it's erratic path to point from noticing to impact, that was under 2 seconds but more than 1 second. I remember reading from Aerocivic that bugs fly over the car and not impacting to windshield, but of course angle of windshield is different, don't know if I should even try to get air to run over the windshield.

There were also some very red birds on road, they seemed not to notice my car very early, had to steer to avoid hitting them when they did set to fly, I did observe clear bump to one, not a hit but air from front of my car kind of boosted the bird up, clear sudden lift as poor bird tried to escape flying to car's path, but still bit too low.

Usually birds fly off earlier, but this species was not the most common that I have seen, so probably it was just species not so used to cars.

I tested also on dusty road, dust behaves differently, I would say dust is now lifted up, bit mixed, but it is not like before where dust did spread all over the road, it is more controlled if one can say so.

Also I did notice that rear window is not getting much of dust or water spray as I did notice when there was wet section of road, water spray is really great for carboard body parts

Not very scientific, but I think they show that there was some change.

Back of car, underside is quite ugly in aero wise, there is car jack and spare wheel hanging from bottom of car, front of those is diesel tank and some other shapes that are not making surface really rough. I did eye that area and if I put some kind of plane there, it will be almost vertical, so that there is not much rise towards rear, this is perhaps good, was 4 degrees for that area some number to seek?

There is not going to be too much of decrease in diameter of car even I put all parts that I can, but I guess that if I can make air leave the vehicle cleanly that would be something worthwhile of effort.

Making such 'fins' as Volt has at rear has been on my mind all the time, maybe I try to create such to near rear lights.

I'm hoping of making kammback addon from clear plastic of some sort, there is 3rd brake light at top of rear window and I wish to leave it visible to other drivers, I think it was 20-30% less chance of being rearended if you have 3rd brake light.

Tomorrow I have 6 hour test drive, I hope to fill up after the drive to see changes immediately, also will be interesting to compare how much I can drive engine off, most of time I drive 50MPH but there are those slower speed areas which are mostly 37.3MPH they are usually very short ones. My average speed on that journey was 46.6MPH to there and back last week according to GPS, average speed is around there for all my trips really, I could go slower, but my trips are so long that I sacrifice bit fuel for time.